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Hormonal Responses to a Fast-Food Meal

For a couple of decades, there has been an ongoing argument regarding the issue of “is a calorie a calorie” in terms of changes on body composition and other parameters.     In that vein is the idea that the body will respond drastically differently to the intake of “fast food” compared to similar meal from organic foods.

To examine this, I want to look at a recent paper titled:

Bray GA et. al. Hormonal Responses to a Fast-Food Meal Compared with Nutritionally Comparable Meals of Different Composition. Ann Nutr Metab. (2007) 51(2):163-71

Which actually made the comparison.  Let’s see what happened.

Yeah, a Calorie is Pretty Much a Calorie

Fundamentally, my belief is that, given identical macro-nutrient intakes (in terms of protein, carbs, and fats) that there is going to be little difference in terms of bodily response to a given meal.  There may be small differences mind you (and of course research supports that) but, overall, they are not large. And certainly not of the magnitude that many make it sound like.

It’s worth nothing that there are a couple of built-in assumptions to my argument, all of which are detailed in the article I linked to above but I want to briefly reiterate them here.

A tediously typical argument of the “a calorie isn’t a calorie” types is usually something along the lines of “Clearly eating 3000 calories of jelly beans isn’t the same as eating 3000 calories of chicken breast and vegetables.”

Well…no shit.

But at that point, the argument is about more than food quality, it’s also about the macro-nutrient content.   And of course the diet containing zero protein will be bad.  But, again that has zip to do with it being clean and everything to do with there being no protein.

My basic assumptions in this argument are that both protein and essential fatty acid requirements are being met.  Beyond that, I find most of the obsession over food quality to be pretty pointless.   At the extremes it might make the tiniest of differences.  In the big picture, it really doesn’t.

Now it’s worth noting that a great deal of the difference seen between “eating clean” and “eating unclean” has to do with caloric intakes.  I’ve pointed out repeatedly that, and this is especially true when people are not counting their calories, certain eating patterns tend to make people eat more than others.  It’s easier to overeat donuts than broccoli.

Clearly, someone eating a 2000 calorie fast food meal will obviously get a different response than someone eating a 500 or even 1000 calorie clean meal.  But as with the argument above, at this point there is more than one variable changing.  It’s not just about clean vs. unclean, you’re comparing meals of drastically different caloric value.

A far more logical comparison would be to look at “unclean” vs “clean” meals containing the same caloric value and the same macro-nutrient content; by controlling those two variables, the only thing being examined will be the quality of the food (rather than the total quantity or the macro-nutrient profile).

Especially when you’re talking about bodybuilders and athletes who are typically controlling their caloric content.  Under those conditions, I argue that there will be no significant difference between the two.  Given identical macros and calories, there is simply no real-world difference in a clean vs. unclean meal in terms of its effects on body composition (health and other effects such as hunger control are separate, albeit important, issues).

However, even there the clean freaks will make the counter-argument: they contend that even if the macros and calories are identical, the unclean meal will still be worse.  This is usually based on an assumed difference in hormonal response (usually insulin).

So who’s right?

Unfortunately, very little research has actually examined this topic in any sort of controlled way (there are at least two studies showing that high sucrose diets generate identical weight and fat losses as lower sucrose diets).    Until now.

Comparing the Meals

The study’s explicit goal was to see if the metabolic response to a fast-food meal would differ to a ‘healthy’ meal of similar macro-nutrient and caloric value.

Towards this end six overweight men and two women were recruited to take part in the study although the data in the women was excluded due to the low number and possible gender effects.

Each subject consumed each of the three test meals on different days with one week in between trials. A standard breakfast was provided at 8am and the test meal was given at exactly 12pm and blood samples were taken every 30 minutes for the first 4 hours and every 60 minutes for the next two hours. Blood glucose, blood lipids, insulin, leptin, ghrelin and free fatty acids were measured.

The test meals consisted of the following:.

  • Fast food meal: A Big Mac, french fries and root beer sweetened with high fructose corn syrup purchased at the restaurant itself.
  • Organic beef meal: this meal used certified organic rangefed ground beef; cheddar cheese; hamburger bun made with unbleached all purpose naturally white flour, non-iodized salt, non-fat powdered milk, natural yeast, canola oil, and granulated sugar; sauce made from canola mayonnaise and organic ketchup; organic lettuce, onion and dill pickles; French fries made from organic potatoes and fried in pure pressed canola oil; and root beer made with cane sugar.
  • Organic turkey meal: this consisted of a turkey sandwich made from sliced, roasted free-range turkey breast with no antibiotics or artificial growth stimulants; cheddar cheese; 60% whole wheat bread made with whole wheat and unbleached all-purpose naturally white flours, non-iodized salt, non-fat powdered milk, yeast, vital wheat gluten, canola oil, and granulated sugar; pure pressed canola oil and canola mayonnaise, stone ground mustard; organic lettuce; accompanied by a granola made with Blue Diamond whole natural almonds, Nature’s path organic multigrain oatbrain flakes, wholesome sweeteners evaporated cane juice, Spectrum Naturals pure pressed canola oil, clover honey, Sonoma organically grown raisins and dried apples. The beverage was an organic orange juice.

So the study was comparing a commercial fast food meal to two carefully designed organic meals (one beef, one turkey) from the above list of ingredients.

The Meal’s Composition

I’ve shown the overall macronutrient composition of the meals below.

Macronutrient Composition of Fast Food and Organic Mals


It’s important to note that while the meals were similar, they were not identical in composition and this is a shame since it makes for a very easy criticism or outright dismissal of the results.  I’ll be honest that I don’t understand why the researchers didn’t put a little more effort into equating the macronutrient composition.

Differences Between the Meals

The biggest difference between meals had to do with the fatty acid composition: the fast food meal contained twice as much saturated and nearly 8 times as much trans-fatty acids with half of the oleic acid compared to the organic beef meal (which is no surprise).

Interestingly, the fast food meal actually contained more linoleic acid than the organic beef meal. The turkey meal had less saturated fat but similar amounts of linoleic and linolenic acid to the fast food meal, with the lowest amount of trans fats.

Hormonal Responses to the Meals

In terms of the blood glucose and insulin response, no difference was seen between any of the meals and this is true whether the data was presented in terms of percentage or absolute change from baseline. The same held true for the ratio of insulin/glucose, no change was seen between any of the meals.

Let’s put it in bold for emphasis.

The blood glucose and insulin response were identical for all three meals despite one being a fast food “unclean” meal and the other two being organic “clean” meals.

Fatty acid levels showed slight differences, dropping rapidly and then returning to baseline by 5 hours in the beef meals but 6 hours in the turkey meal.  Blood triglyceride levels reached a slightly higher peak in the organic beef and turkey meals compared to the fast food meal but this wasn’t significant.

Changes in leptin were not significant between groups; ghrelin was suppressed equally after all three meals but rose above baseline 5 hours after the fast-food lunch but returned only to baseline in the other two meals.

The only significant difference found in the study was that LDL cholesterol decreased more after both of the organic meals compared to the fast food meal, HDL and total cholesterol showed no change after any of the meals. This was thought to be due to differences in the fatty acid content of the meals (saturated fat typically having a greater negative impact on blood lipid levels than other types of fat).

However, beyond that, there were no differences seen in the response of blood glucose, insulin, blood fatty acids or anything else measured.

Limitations of the Study

Now, the study does have a few limitations that I want to mention explicitly.

  1. The study only looked at a single meal.   It’s entirely possible that a diet based completely around fast food would show different effects to one based around organic foods.
  2. The sample size was small: 6 overweight men and two women. It’s possible that differences would have shown up with more subjects. Would a leaner individual respond differently?  I tend to doubt it. But it needs to be studied directly.

However, with that said (along with the fact that the meals weren’t exactly identical), the basic fact is this: the metabolic response between the three meals was essentially identical.  There were no differences in either insulin or blood glucose, the fatty acid profile makes perfect sense given the composition of the meals and blood lipids showed basically no change.

What Do These Results Mean?

This study basically backs up what I’ve been saying for years:  a single fast food meal, within the context of a calorie controlled diet, is not death on a plate.  It won’t destroy your diet and it won’t make you immediately turn into a big fat pile of blubber.  And, frankly, this can be predicted on basic physiology (in terms of nutrient digestion) alone.  It’s just nice to see it verified in a controlled setting.

It’s not uncommon for the physique obsessed to literally become social pariahs, afraid to eat out because eating out is somehow defined as “unclean” and fast food is, of course, the death of any diet.  Never mind that a grilled chicken breast eaten out is fundamentally no different than a grilled chicken breast cooked at home.  To the clean eater/orthorexic they are somehow not the same.

Except that it’s clearly not. Given caloric control, the body’s response to a given set of nutrients, with the exception of blood lipids would appear to be more determined by the total caloric and macro content of that meal more than the source of the food.  This is honestly just basic physiology.

In terms of the hormonal response, clean vs. unclean just doesn’t matter, it’s all about calories and macros.

Which is what I’ve been saying all along.

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