According to the conventional calorie math, the subjects in this over-feeding study should have gained more than a dozen pounds. Is it impossible to overeat protein?
I came across a study on bodybuilders, which suggests that a caloric surfeit doesn´t contribute to weight gain, as you would expect, when the extra calories come solely from protein. Can you comment on it?
The study Fabio asked about was published in 2014 in the Journal of the International Society of Sports Nutrition. And it's definitely worth a closer look
The subjects were all in their early twenties and all engaged in heavy resistance training (i.e, weight lifting). They were quite lean and very muscular going into the study. In fact, if you looked only at their BMI (body mass index), it looked as if the subjects were on the verge of obesity. But when you look at their body composition, it’s clear that the higher body weights relative to their heights were due to high muscle mass.
RELATED: Is BMI an Accurate Way to Measure Body Fat?
One group added a lot of extra protein to their diet in the form of whey protein powder. And when I say a lot, I mean a lot.
These athletes had previously been consuming about 1 gram of protein per pound per day, or about 20-25 percent of calories. This is about twice the recommended minimum intake but comfortably within the acceptable range for protein laid out by the National Academy of Medicine (NAM), formerly known as the Institute of Medicine.
RELATED: How Much Protein Should You Eat?
For the study, the researchers essentially doubled the athlete's protein intake to an average of 300 grams per day, which is quite a bit higher than NAM’s maximum recommended intake. It’s also, as the researchers write, “the highest recorded intake of dietary protein in the scientific literature that we are aware of.”
Nobody is recommending that eating this much protein would be is a good idea on a long-term basis.
The researchers did not evaluate whether this extremely high intake had any negative impacts on liver or kidney function, but many of the subjects complained of intestinal distress. However, nobody is recommending that eating this much protein would be is a good idea on a long-term basis. The point of this short-term study was simply to find out how eating protein in excess of caloric requirements would affect body composition in highly trained people.
The subjects didn’t eat less of other foods; they just added the whey protein on top of what they were already eating. Or at least, that’s how it was supposed to work. In reality, some of the subjects ended up eating fewer carbohydrates, while others actually ate a bit more. But on average, they managed to increase their caloric intake by 800 calories per day. They also continued to do their usual workouts.
So what were the results of this grand experiment? According to the researchers, “the current investigation found no changes in body weight, fat mass, or fat-free mass in the high-protein diet group. This occurred in spite of the fact that they consumed over 800 calories more per day for eight weeks. “
The case of the disappearing calories
How is this even possible? Where did all of those extra calories go? After all, 800 extra calories a day for eight weeks equals 45,000 calories, which, according to conventional calorie math should have translated into a gain of 13 pounds.
And, in fact, when you look at the actual data, you will see that the subjects did gain some weight, but not nearly as much as the old school calorie math would have predicted.
In the group consuming the extra protein, the average change in weight was a gain of almost four pounds. Meanwhile, in the control group, who purportedly changed nothing about their diet or workouts, the average change in weight over the eight week period was a gain of almost two pounds.
The differences between the test group and the control group weren’t large enough to be statistically significant.
Similarly, both groups gained some muscle. The high protein group gained an average of four pounds of lean muscle. The control group gained just three. Both groups also lost a bit of body fat. The high-protein group lost a bit less than the control group.
So how can these researchers conclude that eating the extra protein didn’t lead to any weight gain or changes in body composition? Because the differences between the test group and the control group weren’t large enough to be statistically significant.
Keep in mind as well that this was a relatively small study (only about 30 subjects) and there was quite a bit of variation in the results of the individual subjects. For example, in the group consuming the extra protein, the average change in weight was a gain of almost four pounds. But some of the subjects in this group actually lost weight while others gained twice as much as the average. When the variance in results is that wide, you’d need a lot more subjects before the averages are very meaningful.
Despite all of these statistics-nerd caveats, it’s still somewhat surprising that the group eating all of those extra calories didn’t gain more weight than they did, and that the differences between them and the control group weren’t bigger.
The cost of doing business
Part of the answer to the mystery of the disappearing calories may lie in something called the thermic effect of food. Thermic effect of food refers to the calories we spend digesting and metabolizing our food.
Part of the answer to the mystery of the disappearing calories may lie in something called the thermic effect of food.
In my previous episode on metabolism myths, I described the thermic effect of food as a sort of transaction tax your body charges you to convert the energy in your food into a form your cells can use. It’s a little like changing money in a foreign country. In order to convert your dollars into euros, you have to pay the money-changer a fee. As it turns out, you pay a significantly higher transaction fee to convert protein into energy than to convert carbohydrates or fat. In this sense, all calories are not created equal.
Takeaways for bodybuilders
The thermic effect of food is also significantly higher in muscular individuals than it is in normal or overweight individuals. This may partially explain why these young bodybuilders seemed to burn through all of those extra calories.
As the researchers point out, “it is very difficult for trained subjects to gain lean body mass and body weight in general without significant changes in their training program.”
In other words, if you are very muscular and you want to gain weight (or muscle), simply eating more isn’t going to do it. You’ll also have to lift more. And that’s pretty much what this study demonstrated.
Takeaways for the rest of us
But what does this mean for those of us who are no longer 20 years old with 12 percent body fat?
Overeating on a higher protein diet leads you to gain both fat and muscle while overeating a lower protein diet leads to gaining mostly fat.
Previous studies have demonstrated that feeding people excess calories, even in the form of protein, reliably leads to weight gain. The biggest difference seems to be that overeating on a higher protein diet leads you to gain both fat and muscle while overeating a lower protein diet leads to gaining mostly fat.
Accordingly, here are my takeaways for the rest of us:
Increasing your protein intake may offer several benefits, including gaining or preserving lean muscle tissue, greater appetite control, and a small boost in metabolism, thanks to the thermic effect of food.
But to avoid unintended weight gain, I suggest you reduce your intake of calories from other foods to compensate for the increased calories from protein.