Here's Lyle's comments on the study:
My comments: 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. I've addressed this in articles on my website and the newsletter and have made the basic argument that, given identical macronutrient 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.
And that, along with that, the major differences in body weight or composition seen has more to do with the fact that people tend to eat more under certain conditions than others. That is, 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 at this point, folks end up confounding differences in caloric intake with the quality of the food itself.
In contrast, groups that are obsessed (and I use that word somewhat lightly) with 'eating clean' often make arguments that, somehow, a fast food meal containing an identical amount of protein, carbs and fats as a clean meal containing an identical amount will generate massively different responses (usually in terms of blood glucose and insulin response).
Unfortunately, very little research has examined this in much of a controlled way. Until the paper above came out two weeks ago.
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 macronutrient 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 got all three 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 (I pasted the list from the PDF but took out the source of each of the ingredients).
Fast food meal: A Big Mac, french fries and root beer sweetened with high fructose corn syrup purchased at the restaurant.
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.
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.
The composition of each meal was as follows
Fast food: 1044 calories, 28.2 grams protein, 53 grams fat, 151 grams carbs
Beef meal: 1154 calories, 28 grams protein, 60.2 grams fat, 163 grams carbs
Turkey meal: 1260 calories, 34 grams protein, 49 grams fat, 170 grams carbs
Note: the meals were similar but not completely identical in composition and I think this is one limitation of the study. It would have been better if they'd made the meals identical in both calorie and macro composition.
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.
So what happened. 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. Fatty acids 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.
Now, the study does have a few limitations:
1. It was only examining a single meal. It's entirely possible that a diet based completely around fast food would show different effects.
2. The sample size was small: 6 overweight men. It's possible that differences would have shown up with more subjects. Also, would lean individuals respond differently? Perhaps but I doubt it. I would have liked to have seen the data on the female subjects as there are often gender differences in response.
I guess my main take home message of this paper is that, at least on a single meal basis, fast food is not going to destroy anybody's diet. This is something I've long believed in based on basic physiology (people tend to lose sight of the fact that all carbs eventually turn into glucose, that the difference in protein tend to be fairly negligible for the most part) but it's nice to see it verified in a real world 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' (nevermind that a grilled chicken breast eaten out is fundamentally no different than a grilled chicken breast eaten anywhere else) and fast food is, of course, the death of any diet.
Except that it's 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, not the source.
Which is what I've been saying all along.
