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Comparing the Diets

As happens with most things, the diet world has divided itself up into distinct “camps”, each of which is convinced that their singular approach to eating or fat loss is optimal.  This is nonsense, of course, as best can only be defined relative to the context.  Realizing that, it’s valuable to compare the diets in terms of their pros and cons for different contexts.  And that is what I intend to do.

Introduction to Diets

If you read a lot of diet literature, it seems that there are an endless number of dietary approaches in existence.   However, once you start looking at them in more general, terms you find that this really isn’t the case.    There are only three primary macronutrients that can be adjusted in a diet: protein, carbohydrates and fat.   Within any fixed calorie intake, any time you adjust one, you must adjust another.

And regardless of any other aspect of the diet, how it advocates spacing or timing those meals, what foods are or aren’t allowed, etc. this ends up providing a fairly limited number of dietary approaches in practice.   Because at the end of the day there are only so many combinations available when you have three different nutrients to work with.

So strictly speaking, you can have three macronutrients which could be set at one of three levels: high, moderate and low (I’ll define these terms shortly).   And in premise that would give you 9 possible combinations.    However, one of those options should be eliminated right off the bat.

The Importance of Protein Intake

Before continuing, I want to harp on the issue of protein intake one more time.  Because when I talk about comparing different diets, what I am focusing on are variations in carbohydrate and dietary fat intake.  Protein intakes are assumes to be

  1. Consistent between diets
  2. Set at an appropriate level

This is an important distinction because usually when people claim that a calorie is not a calorie, they are looking at studies where one group ends up eating more protein than another.  And while they tend to focus on the changes in other nutrients, it’s invariably the protein differences that are driving the bus.

So in all cases, you should assume that dietary protein intake is in the range of 1-1.5 g per pound of lean body mass or roughly 2.2-3.3 g/kg.  Thus the only variations between the diets will be in the carbohydrate and fat content since generally that is what is being shuffled around.

The Three Dietary Approaches

While I haven’t really defined what I mean by high, moderate and low, it’s safe to say that most would consider my protein recommendations to be high.  And I’m fine with that.  Alternately, call it moderate.  It doesn’t really matter.  Either works.      What isn’t allowed is a low-protein fat loss diet.   They don’t work and aren’t even worth considering so that’s the option that is eliminated.

As well, for the purposes of this discussion, protein intake will be considered to be fixed at the appropriate level, defined above.  Call it high or moderate, it doesn’t matter. It’s not a variable.  And when you put that into a grid what you end up with is three possible dietary combinations.

The Three Dietary Combinations

So those are the three options here: high carb/low fat, moderate carb/moderate fat and low carb/high fat.

For each of the three you can readily find zealots proclaiming that it is the best and only diet.  Which you can usually translate as “This worked for me”.  Alternately there will be some physiological rationale given for why a given dietary approach is superior to another.

But invariably when you start to look more closely, what you find is that any given diet will have people who got great results, people who got meh results, and people who failed on it completely.    And while there are many reasons that diets succeed or fail, I think a big one has to do with context.  The diet that might be optimal in one situation will not be optimal in another.

Issues such as initial body fat percentage, activity levels, and others will all contribute to whether any specific dietary approach is ideal for a given person in a given situation.   In my opinion, when people find the diet that “just worked for them”, they often stumbled on the one that happened to fit their personal situation.   They ended up the right diet for that context.

But that doesn’t mean that diet is optimal for another person in another situation.  And invariably when someone ends up on a diet that is right for their individual situation, the results are a lot less stunning.  Of course, diet gurus don’t like to talk about the failures even if determining why something didn’t work for someone often provides better information.

And while it would be simple to just tell people “Try a diet until you find the right one” I think that’s a bit of a waste of time.  Rather, I want to compare the three different dietary approaches I have defined above and look at their pros and cons, benefits and drawbacks.  Primarily I want to look at what context they might be optimal for as well as what context they might not be optimal.

This gives dieters a way to hopefully end up on a diet closer to right than wrong for them.  Adjustments can always be made from there.

So, there are three dietary approaches to compare: high carb/low fat, moderate carb/moderate fat and low carb/high fat.  What do those terms actually mean?

Defining My Terms

While I threw around the terms high, moderate and low above, they aren’t particularly meaningful.  One problem you often see in diet literature is that what one person calls high or moderate another call low and vice versa.  There’s not a lot of standardization going on.

Many diets use percentages but I also dislike this as a general approach.  The issue is that percentage can be terribly misleading.  A diet containing nothing but 50 grams of protein per day might be considered “high protein” because protein is 100% of the total calories.   But if you add 2000 calories of table sugar it now becomes a “low protein” diet at only 11% of total calories.     As importantly, it should really be considered a low protein diet because it’s low relative to the body’s physiological requirements.

Put differently, the body doesn’t care about percentages.  Whether it’s 100% of the diet or 11% of the diet, 50 grams of protein is 50 grams of protein.  And whether or not that’s enough (it’s not) depends on the individual, their body size, their activity level and other factors.  Strictly speaking, defining nutrient requirements in g/lb or g/kg is all that really makes sense.

That said, I need some way to delineate the diets from one another.  And while I’m not thrilled with percentages, they will offer at least a semi-objective way to define terms.  Mainly I want to be clear up front what I mean.

First and foremost, protein will be fixed and will represent approximately 30% of total calories.  For the purposes of the calculation that I did I choose a 180 lb individual with 12% body fat who has 158 lbs of lean body mass eating 1.2 g/lb LBM of protein.  This yielded 190 grams of protein which, on a diet of 2700 calories (15 cal/lb) is 28%.

In the chart below, I’ve shown my definitions for both carbohydrates and fat.  I’ve shown reasonably representative percentage definitions along with the number of grams that would be eaten per day assuming a daily intake of 2700 calories/day.  More importantly I’ve shown how what this will represent in terms of g/lb or g/kg since those are the more relevant values to begin with.

Since these are not meant to be hard and fast definitions, I’ve included ranges for most of them.  And yes I am aware that there are empty spots in So carbohydrates jumps from 40% for the high end of moderate carbs to 50% for high carbs.  What do we call 45%?  Moderate?  High?  Does it really matter when we’re talking about 30 grams of carbs either day?  No, it does not.

Definitions of Low, Moderate and High Carbohydrate and Fat Intakes

So you can see that a low-carb diet would be defined as 20% of total calories or less.  On a 2700 calories/day diet this would be 135 g/day or less representing 0.7 g/lb or 1.65 g/kg.  I’d note in this regard that full-blown ketogenic diets are generally defined in absolute terms of 100 g/day of carbohydrates or less.

Certainly some mainstream nutritionists might quibble with the terminology.  For those who think everyone needs 6-10 g/kg of carbohydrates (a value only appropriate for endurance athletes training multiple hours per day), even 5 g/kg might be considered low.  But I’m not interested in their definitions.  These are mine.

In the mainstream, a low-fat diet is usually defined as anything lower than 30% of total calories.  I’ve set it slightly lower since people in the athletic subculture tend to go lower than that.  In fact, many define low-fat as “as little fat as I can eat” and intakes far lower than 75 g/day are not uncommon.

Defining the Diets

With that background, let me define the three “types” of diets that tend to exist.

Comparing the Diets

Since protein is fixed at roughly 30%, leaving 70% of calories for the different combinations of carbohydrate and fat.

The High-carb low fat might range from 30% protein/45% carbs/25% fat up to 30% protein/55% carbs/15% fat.

The moderate-carb moderate-fat diet would range from 30% protein/35% carbs/35% fat to 30% protein/40% carbs/30% fat.

The low-carb high-fat diet would range from 30% protein/20% carbs/50% fat to 30% protein/10% carbs/60% fat.

Now let me look at each in more detail.

The High-Carbohydrate/Low-Fat Diet

For many years, I would say that the high-carbohydrate die has been the go-to recommendation for health, weight loss and athletic performance.   At the same time, it’s quite common to see criticisms of this approach on various grounds ranging from it being unhealthy to being responsible for the rise in obesity.   However, I can’t think of any aspect of nutrition that isn’t surrounded by controversy and carbohydrate and fat intake is no exception.

To a first approximation, both arguments have merit and, as so many things in nutrition, it all depends on context.    The dieter, their activity level, any underlying physiological issues along with how they actually implement such a diet all play a role in whether it will be positive, neutral or negative.

Defining the High-Carb/Low-Fat Diet


Research is finding that, among certain populations, such a diet can do more harm than good. For examples, individuals with insulin resistance tend to get better health benefits from lowered carbohydrates.

Among more fringe diet groups, a diet based around high-carbs and low-fat has become an almost unspeakable evil. Claims that you can’t lose fat on high carbs or can’t get ripped, or whatever, are becoming more and more common.


Now, if you still think of me as the keto-guy you’re probably expecting me to shit all over this diet interpretation or take the fringe stance on it. With some qualifications, I’ll say up front that you’re wrong. The reality is that there are plenty of folks out there who have made high-carb/low-fat diets work and work well.

In fact, over the years it’s probably safe to say that most contest bodybuilders have gotten into shape on such a diet. Folks in the National Weight Control Registry (NWCR, which tracks successful dieters and their habits) reports most using some version of a high-carbohydrate diet (although more recent surveys have identified smaller groups succeeding in the long-term with low-carb diets).

It’d be absurd to dismiss it out of hand even if that’s what most people do.

At the same time, it’s probably safe to say that a lot of folks don’t do particularly well on such a diet, although it depends on a lot of interacting variables. The question is what differentiates the groups: why does such a diet work for some but not others? It’s easy and convenient to say that the drug use among top bodybuilders makes such a diet workable but this is too pat of an answer. Nor does it explain the NWCR folks. In my opinion, the answer is more complex.


Now, upfront I will say that I think a 30/60/10 diet is a little unbalanced to begin with. My main problem is that the dietary fat is too low. As I discussed in Comparing the Diets: Part 1 the technical definition of a low-fat diet is anything less than 30% and the actual government recommended high-carb/low-fat diet is actually closer to 15% protein, 45-50% carbs and 30% fat or thereabouts.

As you might imagine, I find this lacking in protein for body recomposition or optimal athletic performance even if it’s probably ok for the average person (even there recent research supports a benefit of higher protein intakes, approaching 25% for fat loss diets even in the non-athletic). Frankly, my ideal high-carb/low-fat diet would be in the realm of 25-40% protein, 50% carbs and 20-25% fat although, as I’ve discussed before, the percentages themselves are fairly meaningless.

The first problem that typically crops up is that people take a diet that should be ‘ok’ (either 30/60/10 or 15/45-50/30) and screw it up completely. The problem is primarily one of interpretation. It’s not uncommon to see dieters, especially women, turn a 30/60/10 diet into a 10/80/10 diet and they do it by overemphasizing high GI refined junk (the government and researchers thinks that folks are getting their carbs from unrefined grains but this is generally incorrect).

Endurance athletes, who tend to overemphasize carbohydrates frequently do the same thing: many, in my experience, are protein deficient (and studies are suggesting that very low fat intakes can hamper endurance performance). That takes a diet that was right on the edge of being imbalanced to begin with and screws it up even further.

I can track a majority of high-carb diet failures directly to such a mistake in interpretation. And, if you take someone from 10/80/10 to anything else and the results will look like magic. It’s not so much that the new approach is magical as the original approach was screwed up. Just about anything is better than something stupid.

Ignoring this major problem, let’s assume someone actually sets up a 30/60/10 diet more or less ‘correctly’ in terms of amounts. There can still be problems. The first is one of taste. A 10% fat diet is literally a non-fat diet and the small amounts of naturally occurring fats in non-fat foods tend to readily fill up the small fat allotment. Many people find such diets to be tasteless and bland which compromises adherence and research shows that moderate fat diets (discussed in Part 3 of this series) show better adherence than very low-fat diets.

Bodybuilders will just suck it up, of course; they are used to dieting with food that tastes like shit and a common statement is that ‘When I diet, I just make sure I don’t eat anything that tastes good.’ Typical macho crap. But the rest of humanity is unlikely to stick to a diet that they don’t find palatable.

With such an extremely low fat intake, there can also be problems with essential fatty acid intake which can be difficult to meet with so little of a fat intake. Even Dan Duchaine’s high-carb/low-fat diet required 8% essential fats for a total of nearly 18% total fat content (this changed a 30/60/10 diet to 30/52/18 which is damn close to my ideal anyhow).

There is a certain minimal fat requirement, if for no other reason than to ensure adequate absorption of fat-soluble vitamins. Extremely low-fat diets can cause their own set of health problems and this is clearly a place where lower isn’t better.

Another problem that crops up has to do with the types of carbohydrates being eaten. Researchers and other well-meaning types seem to assume that this is going to be the source of carbohydrates among the general public but this is generally not the case. Most of the athletes and bodybuilders who follow such a diet emphasize low GI, unrefined, high-fiber foods; in my experience, most of your typical dieters do not. It’s one thing to eat 60% of your total calories from carbohydrates when all the foods you’re eating have a GI that is extremely low.

As soon as you start making breads, pastas and other high GI foods a larger source of your total carbohydrates you run into a few problems. First is that the speed of digestion is fairly fast, a problem made worse by the low fat intake and generally low fiber intake of high GI food sources (and most people don’t eat enough vegetables or fruit which would provide some much needed fiber). Along with that, the glycemic load (which is the Glycemic Index * the number of carbs eaten)) goes up fast meaning blood glucose can be all over the map. For folks with even moderate insulin resistance (see below) this causes all kinds of problems.

Along with that, most of the higher GI carbs can be surprisingly high in calories. So while 2 oz of uncooked pasta may only contain 40 some odd grams of carbohydrates and 200 calories, an average large bowl of past may easily contain two or three times that. This can easily amount to hundreds of calories. Bodybuilders and athletes are typically obsessive compulsive to begin with, and measure all their food intake; your average dieter is not. So where an athlete will know exactly how many calories they are getting from the pasta or rice, the average person will end up eating too many calories.

That’s ignoring all of the highly refined, high-carbohydrate low-fat foods that food companies brought to market (Snackwell’s anyone?). As above, researchers seem to think that most people are increasing their carbohydrate intake from moderately refined sources but that’s simply not the case in my experience.

As soon as people heard that fat was bad and carbs were good, and food companies rushed high GI non-fat carb foods to market, folks went crazy. Studies even found that, subconsciously, folks figured they could eat more when it was low-fat. Any benefit from lowering the fat content was more than compensated for.

Basically, very high carbohydrate intakes tend to work best when the source of those carbs are low on the GI. If you’re willing to eat almost nothing but low GI carbohydrates in the first place, a high-carb diet will probably work. If not…

Related to this issue is meal frequency. Bodybuilders and athletes eating high-carb diets spread out the carbohydrates over 6 or more meals meaning their total carbohydrate intake per meal isn’t actually that large. That, along with the low GI and high fiber intake minimizes problems with blood glucose swings and the resulting problems. Your average dieter, eating 3 large meals per day, with high GI carbohydrates and too little fiber will generally run into problems with such a high-carbohydrate intake.

Another related issue has to do with activity. Athletes who are burning a tremendous number of carbohydrate calories per day can tolerate/handle many more carbohydrates without problems than someone who is engaging in little to no activity (your average person). This is discussed in detail in How Many Carbohydrates Do You Need?

A bodybuilder or endurance athlete doing 2 hour workouts on a nearly daily basis may be able to tolerate (and may in fact need) such high carbohydrate intakes; someone walking briskly 30 minutes per day three times per week does not.

Related to the activity issue is that of insulin sensitivity. Insulin sensitivity refers to how well (or how poorly) tissues respond to insulin. With high insulin sensitivity, small amounts of insulin generate a large response. With poor insulin sensitivity (insulin resistance), the body has to produce more insulin to get tissues to respond. Recent research has shown a clear link between Insulin Sensitivity and Fat Loss in terms of what diet is optimal.

Individuals who are highly insulin sensitivity handle high carbohdyrate intakes to a better degree than folks with poor insulin sensitivity. I should mention, in this regards, that even folks with substandard insulin sensitivity can sometimes handle high-carbohydrate intakes when insulin sensitivity has been temporarily elevated (such as with glycogen depletion). This is relevant because certain dietary approaches (such as cyclical diets like my Ultimate Diet 2.0) use this ‘trick’: they elevate insulin sensitivity temporarily and then load in lots of carbohydrates before insulin sensitivity goes back to substandard levels.

So what determines insulin sensitivity? Well, there are a lot of factors. First, there’s a genetic component, activity affects it drastically (improving it), so does diet. Diets high in refined, high GI carbs tend to impair insulin sensitivity, so do diets high in saturated fats. Fish oils and unsaturated fats generally improve insulin sensitivity. A crucial determinant of insulin sensitivity is body fat percentage.

Obese individuals frequently become insulin resistant, which causes problems with carbohydrate intakes are excessive (moreso when they are high on the glycemic index). One of the main problems has to do with hunger and appetite. Under conditions of relative insulin resistance, a high carbohydrate intake (especially with very low fat intakes) tends to spike blood glucose levels, which spikes insulin, which crashes blood glucose.

This tends to cause rebound hunger, making calorie control nearly impossible. It also makes people feel crappy with alternating periods of high and low energy. Studies are finding that high-carbohydrate/low-fat diets, especially when the carbs are high on the GI, cause detrimental effects on various health parameters in insulin resistant individuals.

Additonally, some people seem to be carbohydrate ‘addicts’. While it’s debatable whether or not this is a true addiciton, many people find that eating carbohydrates makes them want to eat more carbohydrates. Whether this effect is hormonal or just a taste effect is debatable but it is real.

For such individuals, a high-carb/low-fat diet can cause problems in terms of calorie control. It’s all good and well to tell such people to suck it up, or that dieting is supposed to be a test of willpower, but any diet that makes people feel lethargic and hungry all the time (from crashing blood glucose or simply the ‘taste’ of carbs) is not likely to be followed for very long.

As a final issue, empirically, high-carbohydrate diets can cause problems with stubborn fat mobilzation. The mechanisms are discussed in a later chapter but folks with a lot of lower body fat can have problems getting extremely lean on high-carb diets unless they reduce the GI to very low levels. That means pretty much veggies and the few low GI starches. Women seem to crave carbohydrates more than men and sticking to such a diet can be a losing proposition.

Continued in Comparing the Diets Part 3.

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3 thoughts on “Comparing the Diets

  1. Lyle, I really admire your approach at breaking everything down to the basics, so few experts in their field are able to do that the way that you are. Thank you for always backing your work with scientific data, and leaving out the bullshit extra marketing and hype that you get with most other teachers. I have never experienced work like yours, and I feel blessed to have come across it.

  2. there really is some truth to a different diet for different people i fee like. i used to compete as an amateur boxer and i’d literally have to starve myself to get down my weight. in between bouts my appetite caused my weight to gain easily, in a yo-yo form. mind you i was on a high carbohydrate based diet.

    i finally decided (against conventional wisdom) to switch to an Atkins style diet with ~25% calories from carbs after i stopped boxing. even with little exercise i’ve managed to slim down to a natural walking-around weight close to where i used to box! all my life i was “heavy set” even with tremendous exercise. now i’m in medical school with little time for exercise or even lots of time to prepare my meals. i simply stick with that ratio. and now, no bloating, no rampant hunger, no problems losing fat and keeping it down. i thought i’d pass out with so few carbs like people say but seems my body has a high oxidative (fat burning) capacity, either that or can generate glucose just fine. idk what it is and honestly dont care, been doing this for 2yrs straight. tons of energy

  3. man idk why i stuck to a high carb diet for so long, guess im just stubborn. going down that road even with exercise seemed no other ending than diabetes or hyper/hypoglycemic problems in the long-term

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