## Energy Density

Today I want to cover another fundamental aspect of nutrition that is somewhat easy to confuse.  That concept is referred to as energy density.  Energy density integrates, in a fashion, the concepts of calories, nutrients and food intake (a topic discussed in detail in the article Calories, Nutrients or Food?).

First I want to define energy density before looking at some examples that will hopefully make the concept a bit more clear.  Finally, I’ll look at applications of the energy density concept in terms of dieting, weight gain, etc.

What is Energy Density?

Conceptually, energy density refers to how many calories are found in a given weight or volume or food.  Ok, what does that mean. Let’s say that you have 1 gram of each of the three macronutrients which are protein, carbohydrates and fat.  We know that these are given calorie values of 4 cal/g for protein and carbs and 9 cal/g for fat.  Clearly, in this simple example, fat has over twice the energy density of either carbs or fat (9 cal in one gram vs. 4 cal in one gram).

This basic fact is generally interpreted one of two ways depending on whether a given author is pro- or anti-fat (and of course what the context is).  Pro-fat authors will contend (usually in the context of exercise performance) that since fat contains twice the calories of carbohydrates, it provides more energy to the body on a gram per gram basis (again, the context is usually exercise performance).  While there is an element of truth to this it leaves out some important information that I’m not going to get into in this article.

In contrast, anti-fat authors (usually coming at it from an obesity or weight gain standpoint) tend to blame high caloric intakes (and hence obesity) on a high fat intake because of it’s high energy density.  That is, frequently diets higher in fat are also higher in calories because of the increased energy density.

## Diet Percentages: Part 2

Now that you know how to do the calculations from Diet Percentages: Part 1, in this article I want to talk about some of the problems inherent in setting up diets based on percentages.

Reviewing basic physiology

On a day to day basis, your body has certain nutrient requirements, a topic which is discussed in detail elsewhere in this book. As described in those chapters, those nutrient requirements are generally related to how much you weigh (or how much lean body mass you have). There are a few exceptions, places where the requirements for a given nutrient are absolute which I’ll mention when necessary.

For example, at any given moment, nearly all of the tissues in your body are utilizing some amount of protein for various processes. Your liver, your kidneys, your muscles, your fat cells, your gut are all using protein for protein synthesis and energy needs. Meaning that the more of those tissues you have, the more protein you need; the less of those tissues you have the less protein that you need.

The same goes for carbohydrate and fat. Your body is using energy at some rate (set by your metabolic rate which is fundamentally related to your body mass but also determined by factors such as hormones, the temperature and other factors) and that means providing energy at some level related to bodyweight. Since carbohydrate and fat are your body’s primary energy yielding nutrients, that means that they are required in some amount related to bodyweight. In addition, fat is being used for other structural processes and is going to be required in some amounts relative to bodyweight as well. And although those values may change (based on activity and other factors such as genetics, age, etc.), they are still going to change relative to your bodyweight. Some numerical examples:

The RDA for protein is set at 0.8 g protein/kg body weight (0.36 g/lb) while dieters may need as much as 1.5 g/kg (0.68 g/lb) to avoid excessive protein loss. Endurance athletes need protein at roughly 1.2-1.4 g protein/kg (0.54-0.63 g/lb) and weight trainers may need 1.6-1.8 g protein/kg (0.72-0.81 g/lb). Most bodybuilders use 1 g/lb as a rough estimate and this isn’t too far off from the value of 0.8 g/lb.

So someone who weighs 200 lbs and is sedentary needs about 72 grams of protein per day; if they were dieting, they’d need at least 136 g/day; if they are an endurance athlete, they need between 108-126 grams of protein per day; if they are weight training, they may need 144-164 grams of protein per day. Note, at this point, that I’ve said nothing about percentages.

And while there’s no true requirement for carbohydrates, studies show that maintaining daily endurance performance may take 5 g carbohydrates/kg (2.2 g/lb); glycogen supercompensation requires amounts on the order of 10 g carbohydrates/kg (4.5 g/lb).

For the most part, fat intakes in relation to bodyweight haven’t really been determined, and most research still simplistically talks in terms of percentages. A minimal intake of 3-6 grams of linolenic acid, and 1-2 grams of linoleic acid has been suggested to avoid deficiency syndromes. As discussed elsewhere, whether this represents an optimal amount in terms of health or body recomposition is debatable. Even then, it seems impossible that some fixed amount of either linoleic acid or alpha-linolenic acid would apply to everyone regardless of bodyweight.

But this is all sort of tangential to my point which is that nutrient requirements are related to your bodyweight or lean body mass.

Why is this a problem?

So why is this a problem? When someone puts protein, carb, or fat requirements in terms of percentages only for a diet setup, it doesn’t necessarily have any relevance to what that person actually needs. For example, it’s not uncommon to see diets for bodybuilders set up with 25-30% protein. Others take a more conservative 15% and use that across the board for athletes or general intake. But what do those percentages actually mean? Obviously nothing unless you also know how many calories that person is eating.

Let’s use our 200 lb example individual above and look at his protein intake. Let’s split the middle value for weight training and say he actually needs 150 g/day of protein and put him at two different caloric extremes: 1000 cal/day (a starvation diet) vs. 10,000 calories/day (Parillo style). Let’s set protein at 30% which most would say is sufficient (or excessive depending on who you’re talking to).

1000 cal/day at 30% yields 300 calories from protein, or 75 grams of protein. He’d need 60% protein on 1000 cal/day to get 150 grams of protein per dya. 10,000 cal/day at 30% yields 3000 calories from protein, or 750 grams of protein. Although both diets are 30% protein, the first is half of what our guy actually needs (75 g/day vs. 150 g/day); the second diet has 5 times as much protein as he actually needs. Yes, these are extreme examples and deliberately chosen that way. But they point out that the percentage itself has no relevance whatsoever to what our guy’s actual requirements are.

Now, the typical counter-response to what I wrote above is that the percentage values are assumed to be based on some fairly average caloric intake. That is, if we were to put our 200 lb guy (150 g/protein required per day) on a more ‘average’ 2400 cal/day (12 cal/lb) and 30% protein, he will come out with a protein intake of 2400 * 0.3 = 800 cal from protein yielding 200 grams/day or 1 gram per pound. Yes, a little higher than the 150 g/day but not excessively so. And that’s fine, percentage based diets are going to be roughly valid within a certain caloric range. The problem is that isn’t always how they are applied and that’s certainly not how the percentages are typically interpreted.

More problems: interpretation and usage

It’s quite common to see statements of “Such and such is a high-fat diet and hence bad.” or “High-protein diets are bad”, things of that nature. Most commonly, those statements are based on the percentages of a given nutrient in a diet. For example, diets containing 30% or less total calories from fat are generally considered ‘low-fat’ while, by definition, higher fat intakes are considered high-fat. But this can be terribly misleading as well as misused. Here’s an example.

Let’s say we have a person who’s currently eating 2000 calories of which 150 grams (600 calories) are protein, 176 grams (707 calories) are carbs, and 77 grams (693 calories) of fat. Using the math from the last chapter, this yields a diet that is 30% protein, 35% carbohydrate, and 35% fat. Most would refer to this as a high-fat diet and deem it bad because it contains 35% fat calories. They would probably also call it ‘low-carbohydrate’ and ‘high-protein’ based on the percentages.

Ok, so let’s say we add 200 grams (800 calories) of carbohydrates (let’s use table sugar just because) to the diet without changing anything else. Total calories now go to 2800 and the percentage of calories from fat drops 35% to 25% (protein drops from 30% to 21%, carbs increase from 35% to 53%), even though the total fat intake in grams hasn’t changed. By typical naming conventions a ‘high-fat’ diet has now magically become a ‘low-fat’ diet and nobody will have a problem with the protein or carbohydrate intake, based on the percentages. Of course, total fat intake in grams didn’t change. Neither has protein intake in grams. All we did was skew the percentages by adding 200 grams of table sugar to the diet. And I don’t think anybody would argue that adding 200 grams of table sugar to this diet is particularly healthy. Yet many clueless folks would automatically assume or claim that the second diet (25% fat) is healthier than the first (35% fat) because it’s a ‘low-fat’ diet even though both diets contain the same number of grams of fat.

On a related note, many food companies will use this strategy as well. By simply adding table sugar to a food, to increase the caloric content, they can drive the percentage of calories from fat downwards below 30% and call it a low-fat food. You can make vegetable oil (100% fat calories at 14 grams fat/140 calories) a low-fat food if you add enough table sugar to it. Does that make it healthy because it’s now ‘low-fat’? Obviously not. Or perhaps not so obviously because some folks fixate so hard on the percentages that they miss the forest for the trees.

Using the same starting diet from above, say we decide to take all of the carbohydrates out of the same diet. Now it contains 150 grams of protein (600 calories), zero grams of carbs, and 77 grams of fat (693 calories) and 1293 total calories. Now it contains 46% protein and 54% fat. Most would call this a high-protein, high-fat diet and go into an apoplectic fit even though it contains the exact same number of grams of protein and fat as the previous diet. By simply changing the total carb and caloric content, we can skew the percentages. But we haven’t changed a damn thing in terms of absolute protein or fat intake.

Or an even more extreme example, let’s say we decide to move this guy to nothing but protein (as in my Rapid Fat Loss Handbook). Now he’s eating nothing but 150 grams of protein per day. That’s a 100% protein diet, which most would call ‘high-protein’. First they’d freak out, then they’d tell you that his kidneys are going to fall out of his ass. Except that it contains no more and no less protein than the previously two described diets; once again, by manipulating the total caloric content of the diets we’ve changed the percentages even if we really haven’t changed the gram intake.

On that note, this is a common criticism of ‘low-carbohydrate’ and/or ‘ketogenic diets’. Most will call them high-protein and/or high-fat because the percentage of total calories from protein and fat is very high. But this can be misleading because ketogenic diets are also commonly low in total calories. Studies typically show that total protein and fat intake change very little when people move to ketogenic diets. Rather, total calorie and carbohydrate content come down, and the percentage from fat and protein go up. Nitwit diet critics will look at the high fat percentage and condemn the diet, without looking at the actual gram intake.

Another example: one of the popularly referenced studies by lower-carbohydrate diet advocates refers to a group of athletes given only 40% of total calories from carbohydrates, who are able to maintain performance. This is frequently used (by low-carbohydrate diet proponents) to argue that a diet of 40% carbs is sufficient and/or that ‘high-carb’ diets are unnecessary. Here’s the problem: because of the extremely high total caloric intake in these athletes, 40% of total calories still yielded in excess of 400 grams of carbohydrates per day (a far cry from the 150-200 grams/day you might get on a typical lowered-carb diet). So even though it was ‘low-carbohydrate’ by percentage standards, it was still high-carbohydrate relative to their bodyweight needs. Even at only 40% total calories, they still got close to the 5 g/kg value listed above needed to sustain glycogen stores. Once again, the percentage had absolutely no relevance to the actual gram intake.

And, finally, here’s a rather humorous example from my college days. At some point or another, during a nutrition class, a professor of mine had made the rather common statement that “As long as you don’t eat foods with more than 30% total fat calories, you will be fine” something to that effect. It seemed like a logical extension of trying to get total fat intake below 30%: make sure no individual food contains more than 30% fat calories and you should be safe. At some later date, I took him a cookie recipe of mine that contained approximately 20 calories/cookie and 1 gram of fat (the cookies were mostly air, with a little sugar and some chocolate chips). My professor bristled, because these cookies contained nearly 50% of calories from fat (9 calories out of a total 20). Well, yeah, but they still only contained 1 gram of fat/cookie. ONE GRAM. A cookie that was 200 calories and 30% fat (70 calories) would contain 8 grams of fat even though it’s below the magical 30% cutoff point. Yet he would have considered the second a better food choice based on just the percentage even though it had 10 times as many calories and 8 grams of fat vs. 1. Go figure.

Making my point

Looking simply at the percentages of a given nutrient contained within a diet or food can lead people down entirely incorrect paths. Whether it’s in setting up a diet, on intrepreting a given diet, looking at the percentages alone is a mistake. A 15% protein diet might contain too much protein if calories are absurdly high, and far too little protein if the calories are very low. And a diet which contains ‘only’ 40% carbohydrate may contain more than enough actual carbohydrates by grams as long as the total caloric intake is high enough. A diet which was considered ‘high-fat’ by percentage can be made ‘low-fat’ by simply adding carbohydrates/calories/sugar to the diet but that’s not necessarily improving anything.

As I pointed out early in this chapter and elsewhere, daily nutrient requirements are (generally) based on bodyweight, not the percentage of that nutrient in a diet. If someone requires, say, 1 gram of protein per pound of bodyweight, they need 1 gram per pound whether it represents 10%, 50% or 100% of their total calories. If someone needs 5 g/kg of carbs to maintain performance, that’s what they need whether it’s 40% of their total calories or 60% of their total calories. If they need X grams of fat (X not really having been established at this point except for minimal essential fatty acid requirements), they need X grams no matter the percentage. Are we clear now on the different between percentages and total grams? I certainly hope so.

## Diet Percentages: Part 1

Commonly, when you see diet plans laid out, the intake of the various macronutrients (protein, carbohydrate, fat) is presented in terms of percentages of total caloric intake. So you might see a diet which was 60% carbohydrates, 30% protein and 10% fat or some other set of percentages. Or you’ll see recommendations that ‘…athletes only need 15% of their calories from protein.’ or ‘don’t eat more than 30% of your total calories from fat’, that sort of thing.

In this article, I want to teach readers what these percentages mean and how to use them (if you so desire) either analyze a given diet, set up a diet, or figure out what a food label means.

A quick recap on calories

In a previous chapter I gave you the caloric content of the various macronutrients. To save you needless paging, I’ll review them here.

• Protein: 4 calories/gram
• Carbohydrate: 4 calories/gram
• Fat: 9 calories/gram
• Alcohol: 7 calories per gra

Calculating percentages

With the above values in hand, and using some basic math, we can do several different operations in terms of diet and food analysis. Let’s look at each one in turn. I’ll give examples but don’t read too much into the numbers. They are only examples.

Operation 1: Setting up diets based on percentages

Probably the most common use of methods is to do actual diet set up, to determine how many grams of each nutrient someone will be consuming. Let’s say we have a 170 pound male with a maintenance calorie level of roughly 2700 calories per day and let’s say we wanted to put him on a diet that was 60% carbohydrate, 20% protein and 20% fat (again, don’t read too much into these values, I’m using them for example only). We want to find out how many grams of each nutrient he will be consuming per day.

Step 1: Calculate total calories of each macronutrient

The first thing we’d do is multiply his total caloric intake (2700 cal/day) by the percentages of each macronutrient as this will tell us how many calories will be coming from each nutrient. To convert percentages, just divide by 100 so 20% becomes 0.20, 60% becomes 0.60, etc.

The calculations appear below

• Carbohydrate: 2700 * 0.60 = 1620 calories from carbohydrate
• Protein: 2700 * 0.20 = 540 calories from protein
• Fat: 2700 * 0.20 = 540 calories from fat
• Note: It should be obvious that the percentages need to total 100% (or 1.0).

Step 2: Determine total grams from each macronutrient

Now we simply divide the total calories from each macronutrient by the caloric content of each macronutrient. This tells us how many grams of each food our guy will be eating each day.

• Carbohydrate: 1620 calories / 4 cal/gram =405 grams carbohydrate
• Protein: 540 cal / 4 cal/gram = 135 grams protein
• Fat = 540 calories / 9 cal/gram = 60 grams fat per day

So this particular diet, with 2700 calories and 60% carbs, 20% protein and 20% fat yields a diet of 405 grams of carbohydate, 135 grams of protein and 60 grams of fat per day. For the remainder of the diet setup, you’d divide that up across some number of meals including pre- and post-workout, all that jazz.

Operation 2:
Working Backwards Part 1: Determining Diet Composition

You can just as easily work the math backwards, to determine what percentage of each nutrient a given diet is. Let’s say someone was eating 150 grams of protein, 200 grams of carbohydrate, and 50 grams of fat and we want to find out how many total calories they are eating and what the percentages of the diet are.

Step 1: Determine caloric intake

First you simply mutiply the total grams of each nutrient by the caloric content of that nutrient. That tells you how many calories they are eating each day

• Protein: 150 grams * 4 cal/gram = 600 calories from protein
• Carbs: 200 grams * 4 cal/gram = 800 calories from carbs
• Fat: 50 grams * 9 cal/gram = 450 calories from fat
• From those values, you can calculate total daily caloric intake by simply adding up the numbers.
• Total calories = 600 + 800 + 450 = 1850 calories per day.

Step 2: Determine percentage from each nutrient

Now simply divide the calories from each nutrient by the total number of calories being consumed to determine the percentage each nutrient is providing. Multiply the decimal amount by 100 to get the percentage

• Protein: 600 calories/1850 calories = 0.32 * 100 = 32%
• Carbs: 800/1850 = 0.43 * 100 = 43%
• Fat: 450/1850 = 0.24 * 100 = 24%.

So our example person is consuming 1850 calories per day with 32% from protein, 43% from carbs and 24% from fat.

Operation 3:
Working Backwards Part 2: Determining Food or Meal Composition

You can use the identical math above to determine the composition of a given food (based on the food label) or a given meal.

So say you wanted to determine the macronutrient percentages on a food or a meal that contained 10 grams of protein, 20 grams of carbohydrates, and 9 grams of fat.

Step 1: Determine calories from each nutrient

First you’d simply multiply the total grams of each nutrient by the caloric content of that nutrient.

• Protein: 10 grams * 4 cal/gram = 40 calories
• Carbohydrate: 20 grams * 4 cal/gram = 80 calories
• Fat: 9 grams * 9 cal/gram = 81 cal

Although most food labels list the total caloric content, even if they don’t, you can easy figure it out by adding up the totals above. This food/meal would contain 201 calories (40 cal + 80 cal + 81 cal)

Step 2: Determine percentages from each nutrient

Now you simply divide the total calories from each nutrient by the total calories in the food.

• Protein: 40 calories/201 calories = 0.2 * 100 = 20% calories from protein
• Carbohydrate: 80 calories/201 calories = 0.4 * 100 = 40% calories from carbohydrate
• Fat: 81 calories/201 calories = 0.4 * 100 = 40% calories from fat

So this food or meal would contain 201 calories, with 20% protein, 40% carbs and 40% fat. Whether those percentages mean anything is the topic of the next chapter

A note on food labels

Many people become perplexed when they do the math above on food labels and find that the caloric content listed isn’t the same as what they calculate. So you might see a food that was listed as containing 212 calories with 10 grams protein, 20 grams of carbs and 9 grams of fat (which, as above, only yields 201 calories). There are a couple of reasons that this happens.

The first is that determining the caloric content of a given food isn’t doesn’t give perfect values, there is always a little bit of slop. As well, the 4, 9 and 4 cal/g values are rounded values in the first place. Finally, food labels almost always round off the values for protein, carbs and fat grams (for example, a food containing less than 0.5 g of fat can list it as 0 grams of fat). If the food listed above actually contained 10.5 grams of protein (44 calories), 20.5 grams of carbs (84 calories) and 9.5 grams of fat (85 calories), that would make up for the difference in values.

Ultimately, these types of tiny differences are no big deal. Even under the best circumstances, caloric estimates are only estimates and there’s always going to be a little bit of slop either direction. We’re not doing clinical nutrition here and, as long as it’s not excessive, small discrepancies in calore values are nothing worth worrying about.

In Diet Percentages: Part 2, I’ll explain why I think using percentages to set up diets is a mistake.

## Carbohydrate and Fat Controversies: Part 2

In Carbohydrate and Fat Controversies: Part 1, I begun an examination of the argument over carbohydrate and fat intakes in the human diet, explaining that, contrary to popular argument, most extremist stances in this debate are incorrect. In Part 2, I want to continue addressing the issue by looking at both sides of the debate.

Examining Both Sides of the Debate

As noted, the usual argument goes that high-fat diets cause high-cholesterol, heart disease, cancer, obesity and the rest, as evidenced by the high incidence of those disease in modern diets (which are typically high in fat). But that’s a questionable conclusion to draw.

Modern diets are also high in carbohydrates (and mainly the highly refined, high GI, low-fiber stuff that the body often doesn’t handle well), low in fruits and vegetables, and generally contain the wrong types of fats (an excess of saturated and trans fats with insufficient amounts of healthy fats). Such an intake is typically coupled with inactivity, the folks eating them tend to be overweight/obese, smoking and alcohol play a role, etc. That is, there are a number of inter-related factors at work here.

Pinning the blame entirely on fat intake or expecting only a reduction in fat to fix the problem is disingenuous: there are a lot of variables at work here. Some research suggests that the entirety of the problem rests with excessive saturated fat intake with the other variables (activity, fruits and vegetables, etc.) playing a relatively minor role. It’s awfully hard to tease out all of the relationships when there are this many variables at play.

Similar comments can be made in terms of obesity. Fat is more calorically dense than carbohydrates and studies comparing high-fat (40%) to low-fat (25%) meals find that people tend to eat more in the higher fat conditions; this is usually referred to as passive over-consumption and leads to excess calorie intake. These studies have problems, mind you, but that’s beyond the scope of this article. The point does stand, though, that dietary fat is tasty (giving food mouth feel) and folks do tend to eat more of foods that taste good.

But while it’s common to blame obesity on high-fat diets, not all researchers agree. Some cultures have fairly high fat intakes but have no problems with obesity and researchers are starting to realize that fat isn’t the ONLY problem. Increasing intakes of refined carbohydrates (contributing large numbers of calories to the diet), decreasing activity, increasing portion sizes and other factors all contribute. You can’t dismiss an excessive fat intake as part of the obesity problem; it’s simply not the sole factor. I don’t want to get into a massive discussion of the carb versus fat debate in terms of caloric intake, preferring to focus on the health issues here.

The fact is that not all studies link a high fat intake to an increased risk of disease. For example, recent analyses of our ancestral diet (what we ate during 99.9% of our evolution) suggests a much higher fat intake and much lower daily carbohydrate intake. Exact numbers vary depending on what assumptions you use but carb intakes of 20-40% (most of which came from low GI, high fiber fruits and vegetables; grains were almost non-existent), fat intakes of 28-60% (which had a significantly different quality than our current diet), and protein intakes of 19-35% of total calories are the current best estimates.

Studies of extant hunter-gatherer societies show little incidence of any of the diseases of modern society and it’s thought that our evolutionary diet was NOT atherogenic (promoting heart disease) despite the high fat intake.

The reasons for this are many-fold, of course and that’s the key to keep in mind when you consider fat intakes and potential health problems. In our ancestral diet, fiber intakes were monstrous, averaging 100-150 grams per day. As well, despite the high fat intake, the source of that fat was far, far different than our modern intake. Much higher intakes of polyunsaturated and mono-unsaturated fats and far lower intakes of saturated fat were fairly typical. Activity levels were also much higher and folks generally stayed pretty lean. Alcohol intake was low or non-existent, as was smoking. Although our ancestors dealt with various stresses, they didn’t deal with the kinds of chronic stress that occurs in modern societies.

Related to this, studies of the Mediterranean diet have found few problems in terms of heart disease and all the rest despite a relatively high fat intake (40% of total calories). Although the reasons are, as always, multi-factorial some of the contributing factors are that the fat intake is primarily from mono-unsaturated sources (e.g. olive oil).

As well, a tremendous amount of fresh vegetables are typically consumed (with far less reliance on refined carbohydrates). Other factors such as activity, bodyweight, moderate alcohol intake and lowered stress levels probably play a role. Studies of the Alaskan Inuit show similar results, despite an extremely high-fat intake, heart disease is almost unheard of. This has typically been attributed to the high intake of fish oils but there may be genetic adaptations as well.

Of course, some studies on low-carbohydrates diets (which are typically high in fat) will show a big improvement in blood lipid levels; this is especially true for individuals with insulin resistance. I’d note that this effect primarily occurs when weight is lost; in studies of very low-carbohydrate diets where weight is gained, blood lipid levels often get much much worse.

Thus, whether or not you’re gaining or losing weight probably impacts on whether or not dietary fat is a health risk. I’d note that studies in cyclists find that high intakes of saturated fat don’t pose a health problem as long as the athletes are in calorie balance. As I mentioned above, activity (which will affect whether ingested dietary fat is stored or burned off) plays a big role here.

Studies in diabetics are finding that higher mono-unsaturated fat intakes (and lowered carbohydrate) intakes may be healthier than the converse. This, of course, only holds if calories are strictly monitored and controlled to avoid weight gain. When weight is gained, from nearly any dietary approach, blood sugar control in diabetics worsens.

Of course, there’s a flip side to the anti-fat dogma and reducing fat to extreme levels can cause its own set of problems. First and foremost, most people find extremely low-fat diets to be tasteless and this tends to limit adherence in the long-term (as I mentioned above, high-fat diets tend to be very tasty and people frequently eat too much).

And while caloric intake typically goes down in the short-term, folks frequently end up increasing caloric intake because they are hungry all the time. Dietary fat slows gastric emptying (keeping food in the gut longer) although some work suggests that this effect is lost with chronically high-fat diets. Extremely low-fat diets tend to leave people hungrier for this reason.

There is also evidence that the fat-soluble vitamin absorption may be impaired when fat intake is taken too low. And while total cholesterol typically decreases when fat intake is lowered, the decrease occurs in both the good (HDL) and bad (LDL) sub-fractions so overall health risk may not be improved. From a body recomposition or performance standpoint, some studies show a lowering of testosterone with very low fat diets.

There is another set of issues that crops up as well. Again, it relates to the simple fact that people have to eat something. In reducing fat intake, most people increase carbohydrate intake. Most researchers would say that this is just fine as long as the increase comes in the form of unrefined, high fiber, complex carbohydrates. I would say that most researchers need to get out of the lab and look at the real world for a while.

The simple fact is that the majority of people who reduce fat do NOT increase carbohydrate intake from unrefined, high-fiber, complex sources. This is especially apparent in the US (I can’t speak for other countries) where companies rapidly jumped on the ‘fat is bad’ bandwagon and brought tons of ‘low-fat’ high-carbohydrate sources that were highly refined to market.

Such foods may have as many, if not more, calories than the same higher-fat items. Even when they don’t, humans play a cute psychological game, tending to eat more of a given food when they are told it’s low or no-fat.

Recent studies are finding that, when carbs are increased from those sources, other problems show up. In addition to the changes in blood cholesterol I mentioned above (both the good and bad subfraction decrease), the increase in refined carbohydrate intake causes an increase in blood triglyceride levels and small LDL particles; both of which are independent risk factors for heart disease and all the rest. The chronically high insulin levels which commonly occur with such a diet cause other problems including insulin resistance and all of the issues that accompany it.

I should probably note, and this could certainly be an entirely separate article, that the new scapegoat for obesity and all of the health problems in the world is excessive carbohydrate intake, with a lot of the focus on insulin release. I don’t have space here to address that side of the argument, a future topic for another day.

Sufficed to say that while there is certainly an element of truth to this (in that excessive intakes of any nutrient, and that includes refined carbohydrates, is bad), it’s still true that simplistically arguing that ‘fat is good and carbs are bad’ is just as moronic as arguing that ‘carbs are good and fat is bad’. Again, it depends on the context.

Summing Up

Now, I want to make it very clear that I’m not trying to make this either a pro-fat or anti-carbohydrate article or trying to make a low-carbohydrate diet the default choice for anybody. My point is simply that the idea that ‘fat is bad’ and ‘carbs are good’ (or the opposite) is too simplistic to be meaningful.

Not all fat is bad and not all carbs are good. The source, the composition of the rest of the diet, the total amounts you’re eating of each, your activity level and other variables all factor in. Whether you’re talking about health risk or obesity, you can’t simply pin the blame on one factor or the other.

So, under conditions of high caloric intake, with a high intake of refined carbohydrates (meaning chronically high insulin levels), poor quality fat choices (too much saturated fat and/or too little unsaturated fats), little activity, minimal fruit and vegetable intake, etc. a high-fat intake is probably very detrimental from a health standpoint. Sadly, this describes a fairly typical diet in the modern world (especially the US).

In contrast, with reduced or even controlled caloric intake (such that bodyweight goes down or is maintained) and most of the fat coming from unsaturated sources (note: excessive polyunsaturated fats has its own set of problems), a high fruit and vegetable intake, reasonable activity levels, keeping body fat levels down, etc. higher fat intakes may be no problem at all. In some situations, an increased fat intake (again, from healthy sources within the context of activity and a high fruit and vegetable intake) may be beneficial compared to the alternatives (e.g. increasing carbohydrate intake).

## Carbohydrate and Fat Controversies: Part 1

Although there are still many Protein Controversies (usually regarding kidney health, bone health, etc.), nowhere in the dietary world is there quite as much controversy as over carbohydrate versus fat intakes.

In this article, I want to look at carbohydrate and fat intake in terms of the various arguments and debates that tend to surround them.

The main controversy here revolves around what amounts of carbohydrates and/or fat are ideal, healthy, recommended, etc. and that’s what I’ll focus on. I’m not going to deal with body composition explicitly in this article, I’ll save that for another day.

Two (or Three) Dietary Camps

Generally, folks fall into one of two camps regarding whether they think carbohydrates or fats are good or bad. For a couple of decades now, the mainstream of dietary advice has been more or less stuck in the mindset of ‘fat is evil and ‘carbohydrate is good’.

Various attempts to promote so-called ‘high-fat’ or ‘low-carb’ diets have usually been shot down as fads although there is increasing research evidence that, at least for some individuals (usually those with insulin resistance) higher fat intakes and lowered carbohydrates may be both beneficial and preferred.

However, for the most part, I’d say that mainstream dietitians are still on the carbs = good, fat = bad bandwagon with higher fat/lower carbohydrate diets being relegated to the diet ‘fringe’.

Both groups can bring impressive (or at least impressive looking) data to the table but, as usual, extreme stances are invariably incorrect and the truth lies somewhere in the middle; this particularly debate is no different.

The third group (and the one I put myself in) recognizes that whether or not carbohydrates or fats are ‘good’ or ‘bad’ depends on the context. The source of the carb or fat, the rest of the diet, the goal of the individual, genetics, activity, etc. all factor into this issue. So while it may be convenient to give simplistic recommendations of the ‘X is bad, Y is good’ variety, simple in this case tends to be incorrect.

Perhaps the most succinct way of describing what I’m going to detail is that there are no good or bad foods only good or bad diets. That is, within the context of one type of diet or individual situation, a specific food may be excellent; under other conditions it may be a poor choice.

What does the Body Require?

So that some of my comments will make sense, I need to cover a smidgen of nutrient physiology, mainly having to do with the issue of carbohydrate ‘requirements’ (a topic I cover in detail in How Many Carbohydrates Do You Need).

As I think I’ve managed to work into every book I’ve ever written, there is no strict physiological requirement for carbohydrates (this factoid is often used by the low-carb diet groups as part of the rationale for their dietary approach).

Most tissues in the body can readily use fatty acids for fuel just as easily as glucose. There are a few tissues such as the renal medulla, red blood cells and one or two other that can only use glucose. However, those cells essentially make their own glucose by recycling lactate (produced from glucose metabolism) back into glucose.

The brain is in its own weird category. Under most conditions, it relies exclusively on glucose. And while it can’t use fatty acids directly, it can use a fatty acid derived fuel in the form of ketone bodies. After roughly three weeks of adaptation to using ketones, the brain may only need 25 grams/day of glucose or so, which can be made by the body (in the liver and kidney) from sources such as lactate, pyruvate, amino acids and glycerol.

Even the American Dietetic Association bible, the RDA Handbook, states that there is no requirement for dietary carbohydrates. Any decent nutrition or physiology book will state the same. Despite this basic biological fact, many researchers and diet authorities still insist that the majority (50-60% or more) of the human diet should come from carbohydrates.

I’ve seen papers where researchers point out that the body requires no carbohydrates which then go on to say that a proper diet should contain at least 50% carbohydrates. It doesn’t make much sense.

At the same time, outside of a small essential fatty acid requirement (a few grams per day from the fish oils, EPA/DHA), fats aren’t truly required by the body either. All of the tissues I mentioned above will use glucose if you provide it (the heart is an exception, almost exclusively relying on fatty acids for fuel) and the body can make fatty acids out of other sources if need be (this pathway isn’t utilized massively in humans, although a few conditions will make it relevant).

So, outside of the small essential fatty acid requirement, one could make an argument for there being no physiological requirement for fats either.

What does the body then require on a day to day basis if there is no real requirement for either carbohydrates or fats? Well, outside of the basics like water and air, roughly eight amino acids are essential to get from the diet, there’s the small essential fatty acids requirements and of course vitamins and minerals. Everything else, strictly speaking is optional.

I would note that, to avoid starving to death, sufficient calories will be required. Since it’s generally unrealistic to consume your entire daily caloric requirement from protein, that means that carbs, fats, or a combination of the two, will generally be needed to supply sufficient energy to the body.

But, as noted above, most tissues in the body show a great deal of flexibility, using carbs when they are available and fats when carbs aren’t available. Note also that the body has its own store of fuel, primarily in the form of body fat that is mobilized when sufficient amounts of other nutrients aren’t available.

So Why Do Most Argue that Carbs are Good and Fats are Bad?

Despite the fact that there is no physiological requirement for carbohydrates in the human diet, the most common dietary recommendation in modern times is generally to reduce fat intake and increase carbohydrate intake. I’m going to address the issue starting from that standpoint.

A good question might be why is this stance taken. While I can’t read the minds of these folks (and I hate to contribute to grain lobby USDA conspiracy theories), I think the reasons is actually fairly simple: we have to eat something.

There’s usually a limit to how much protein can be reasonably consumed (and most authorities seem to be against ‘high’ protein intakes as well) so that means that the rest of the diet (in terms of energy) must come from either carbohydrate or fat.

In the 70’s, the stigma against dietary fat started to develop and it all pretty much went from there. Fat was implicated as the cause of heart disease, stroke, obesity, you name it and excessive fat intake was blamed.

Since people have to eat something and because of the general stigma against a high fat intake (some of which is warranted, some of which isn’t), policy makers recommend a high-carbohydrate intake by default.

The bigger question is whether or not this is a scientifically defensible position.

I’ll address this issue in more detail in Carbohydrate and Fat Controversies: Part 2