Eating tons of protein won't make you fat. Here's why.
Nearly every dietitian tells you that eating extra protein leads to extra body fat storage, just like it does with excess carbs and fats. After all, a calorie is a calorie.
But they're wrong. The truth is, eating a lot of protein, even up to 5.5 times the RDA, won't make you gain any additional fat, even if all that protein adds calories to your diet. Instead, it seems to have a protective effect against fat during periods of increased calorie intake while also leading to additional muscle mass, provided the circumstances are right.
230g, no lifting, 7 pounds of lean mass
Overfeeding carbs or fat results in body comp changes that are different from overfeeding on protein. Dietary protein has a protective effect against fat gain during periods of overeating. How protective?
In one study, researchers randomized subjects to partake in one of three diets:
- Low protein (5%) – Around 47 grams daily
- Normal protein (15%) – About 140 grams
- High protein (25%) – Around 230 grams
Randomized subjects were then "force-fed" 140% of their maintenance calories – about an extra 1,000 calories for 8 weeks straight.
Carb intake was kept at about 42% between the groups, while dietary fat ranged from 33% in the high protein group to 44% and 52% in the normal and low protein groups, respectively.
After doing their DEXA magic, the scientists found that while all subjects gained approximately the same amount of fat (the high protein group gained a little less than the other two groups), the high protein group gained about 7 pounds of lean mass.
We know what you're thinking: "Hey, all three groups gained the same amount of fat. Where's this alleged protective effect of protein?"
Slow down. The participants were not resistance-trained. That extra 7 pounds of lean mass fell on them like manna from heaven. Clearly, their results showed that excess protein during an overeating phase contributed to lean body mass gains. That throws a high-protein pie in the face of all those dietitians who still insist that a calorie is a calorie.
But what would happen if someone took it one step further and conducted a similar study, but this time with resistance-trained athletes and an even higher protein intake?
5.5 times the amount of protein
Dr. Joey Antonio wanted to determine the effects of a very high protein diet (4.4 g/kg/d) on body composition in weight-training men and women.
The study design was simple: Thirty healthy weight-lifting people were randomly assigned to a control group or a high protein group. The control group maintained their same training and diet over an 8-week period. The high-protein group also maintained their same training and diet (same carb and fat intake), but with the added instruction to eat 4.4 grams of protein per kilogram of body weight (5.5 times the RDA).
The high-protein group would be eating around 800 calories per day more than the control group. These additional calories were all from protein.
Here's the clincher: After 8 weeks, despite eating 800 extra calories per day – all of it from protein – the high protein group experienced no changes in body weight, fat mass, or fat-free mass.
You probably have mixed feelings about those results. On one hand, you're probably elated that all those extra calories from protein didn't result in any additional tubbiness. However, you're probably disappointed that it didn't lead to any additional muscle mass. Read on for a clearer picture.
Some rationalization
In the first study, the untrained folks gained 7 pounds of lean mass just by increasing protein intake to 230 grams per day. No exercise was involved, so this suggests they weren't getting enough protein to begin with, which casts dark aspersions on the U.S. recommended daily amount of protein (about 63 grams for a 175-pound person).
That brings us to Antonio's study: Why did the high protein group, despite ingesting 5.5 times the RDA for protein, fail to gain any lean mass, let alone fat mass? In a nutshell, because they were already working out, and it's very difficult for trained subjects to gain lean body mass without significant changes in their training program, especially in just 8 weeks. Add a few more months and a bodybuilding-focused training plan, and we'd have seen gains in lean body mass.
Why won't protein turn into body fat?
Well, it can, but it's unlikely. Biochemically, turning dietary fat into body fat is easy, and turning carbs into body fat isn't that much more difficult.
Turning protein into body fat, however, is an entirely different type of challenge. It takes several biochemical and hormonal steps, and it's monitored closely by the liver, which metes out amino acids according to the body's metabolic needs (tissue breakdown, tissue synthesis, catabolism, anabolism, etc.)
As such, protein has a protective effect against fat gain in times of caloric surplus, particularly when combined with lifting.
How to use this info
Here's what we think you should take with you:
- Regular, non-training people should probably throw the 0.8 grams of protein 15 per kilogram RDA out the window and strive for at least 50% more.
- As a lifter, you likely need to eat more protein; maybe not 5.5 times the RDA, but maybe more than what you've previously believed to be adequate. The added calories won't turn to fat.
Lastly, it's probably impossible to eat that much extra protein from whole food sources. You must, as the subjects in Antonio's study did, augment whole-food protein choices with a quality protein powder, like MD Protein > Buy at Biotest.
A simple fix? Adopt a protein-first eating strategy: just add one or two protein shakes to your daily diet and well, the rest pretty much takes care of itself. More info here: The protein-first diet strategy.
References
- Antonio J et al. The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals. J Int Soc Sports Nutr. 2014 May 12;11:19. PubMed: 24834017.
- Leaf A et al. The Effects of Overfeeding on Body Composition: The Role of Macronutrient Composition – A Narrative Review. Int J Exerc Sci. 2017;10(8):1275-1296. PMC: PMC5786199.
- Bray GA et al. Effect of protein overfeeding on energy expenditure measured in a metabolic chamber.
- Am J Clin Nutr. 2015;101(3):496-505.