How Much Protein do you Need to Lose Fat?
Updated: May 10
Let's talk about protein intake and fat loss.
The Recommended Dietary Allowance (RDA) for protein is 0.36g per pound (or 0.8g per kilogram) of bodyweight (for adults). That’s not a lot and if you’re looking to make favourable changes in body composition by going on a calorie-restricted diet then you may want to go higher. In fact, there are numerous studies, which suggest this is a good idea.
In a study presented in the journal, Obesity, 43 men who were overweight or obese were split into two groups. Both groups were put on a calorie-restricted diet for 12 weeks.
One group consumed the RDA for protein. This provided about 15% of their total calories for the day. The other group consumed 0.63 g/lb of protein, which worked out to about 25% of their daily calories.
Both diets consisted of about 25% of total calories coming from fat, while the remainder came from carbs. So, fat intake was consistent between both groups, but protein and carb intake varied.
After the 12 weeks, the researchers found that both groups lost about the same amount of weight and body fat. The group that consumed more protein retained significantly more lean body mass tho. (Note: Lean body mass is a collective term that includes muscle, water, blood, bone, organs and other tissues in the body. Basically, anything that’s not fat in your body.)
In another study, 103 men and women were divided into two groups. Both groups followed a calorie-restricted diet for four months. The diets consisted of 30% fat, however, the protein (and therefore carbs) varied. One group consumed the RDA for protein, while the other consumed twice this amount (0.72g of protein per pound of bodyweight).
The results showed that both groups lost about the same amount of weight, but those who consumed a higher protein intake lost more fat.
In a third study, which I wrote about in the article “Are 6 Meals a Day Better than 3 for Fat Loss”, supports the need for a higher protein intake as well. Actually, this was an interesting study with a unique design and outcome.
The researchers split overweight individuals into three groups and had them consume an energy-balanced diet (i.e. the amount of calories required to maintain one’s weight, a.k.a. a maintenance diet) for 28 days. The difference between the groups was that one consumed 15% of the calories from protein, while the other two consumed 35%. (Note: The difference between the two latter groups was one ate three meals a day while the other consumed six.)
What they found during this time was that those who ate 35% of their calories from protein lost a significant amount body fat when compared to those who consumed 15%. Yep, those who ate 35% calories from protein lost body fat on a diet designed to maintain their weight. (So that’s awesome.) Just keep in mind tho that this was just one phase of the study.
Following the energy-balanced diet, the subjects were then put on a calorie-restricted diet for another 28 days. Their calorie intake was reduced by about 25%, but the groups consumed the same percentage of protein that they did during the previous phase (15 or 35%). So, the percentages were still the same, but the overall amount of protein for the day was lower when compared to the previous phase.
After the 28 days, the researchers found that all groups lost body weight, but the two groups who consumed more protein for the day lost significantly more body fat than those in the 15% group.
The three studies mentioned above were conducted on individuals who were not overly active. So, let’s look at what happens when you factor in exercise.
In a four-month study, 48 obese women (40-56 years old) were divided into four groups. Each group was put on a calorie-restricted diet. The diets were equal in the total amount of calories, but differed in their protein and carb content (fat was kept at 30% of total calories for all diets).
Two groups consumed the RDA for protein with the remainder of their calories coming from carbs. The difference between these two groups was that one followed an exercise program (five days of walking and two days of resistance training) while the other did not.
The two other groups consumed twice the RDA for protein with the remaining calories coming from carbs. Likewise, one group followed the same exercise program while the other did not.
The results showed that all groups lost weight, but those who consumed twice the RDA for protein lost more weight and fat mass. Out of those two groups, the one that followed an exercise program lost more weight and fat mass, while also preserving more lean body mass.
As you can see, there’s a strong argument for overweight and obese individuals to eat more protein. That and an exercise program is a good idea too. But what about leaner individuals? Well, they look to need even more. Here’s a few reasons why.
In a 4-week study, 20 young, resistance-trained individuals were split into two groups. For the first week of the study, the subject’s calorie intake and output was assessed. During the second week, the subjects followed a maintenance diet based on the findings of the previous week. In weeks three and four, the subject’s calorie intake was reduced by about 40%. The difference between groups was that one consumed 0.45g/lb. of protein a day while the other consumed 1g/lb. Also, worth noting is that they were training throughout the study.
What the researchers found was that both groups lost about the same amount of fat, but those who ate less protein lost more lean body mass (3.5 vs. 0.7 lbs.). Yikes!
So, at this point, I feel confident I’ve convinced you that the RDA for protein is not adequate, but how much protein is enough? Well, a 2013 study may shed some light on this question.
In this study, researchers divided 39 recreationally-fit adults into three groups. All three groups were put on a calorie-restricted diet for 3 weeks. Total calorie intake was decreased by 30% and physical activity was increased by 10%. Thus, providing a calorie deficit of 40%.
All diets provided 30% of calories from fat. The difference between diets, as I’m sure you’ve already guessed, was protein content.
One group consumed the RDA for protein. The second group had twice this much, while the third group had three times this amount. Worth mentioning is that all groups followed a cardio- and weight-training program, but it wasn’t all that intense.
After three weeks, the results showed that all three groups lost the same amount of weight, but the groups who consumed more than the RDA for protein lost significantly more fat and less muscle mass. Seems to be a common outcome. ;-)
Interestingly, the results between those who ate two and three times more protein weren’t all that different in this case. I’m curious to see if an intense training program would show a different outcome tho.
So, what’s the reco on protein content for a calorie-restricted diet? Well, there’s quite a few and they’re generally listed in ranges.
For example, a 2016 review published in the journal, Applied Physiology, Nutrition, and Metabolism, suggests a protein intake between 0.68-1g/lb for the general population.
A 2011 review by Phillips et al. suggests a protein intake between 0.8-1.2g/lb of bodyweight for athletes in a calorie deficit. While a review in the journal, International Journal of Sport Nutrition and Exercise Metabolism, suggests a protein intake between 1.1-1.4g/lb of fat-free mass for lean, resistance-trained individuals consuming a calorie-reduced diet.
I generally hover around a gram per pound of bodyweight, but will adjust depending on a few variables (body fat, activity levels, calorie deficit, etc.).
And there you have it. While your daily caloric intake will have the greatest influence on whether you lose weight, it’s the macronutrient composition of those calories (with an emphasis on protein content), which will influence whether that loss is coming from fat or muscle.
And now you know. :-)
For more information:
1. Tang, M. et al. Normal vs. high-protein weight loss diets in men: effects on body composition and indices of metabolic syndrome. Obesity (Silver Spring). 2013. Mar;21(3):E204-10.
2. Layman, DK et al. A Moderate-Protein Diet Produces Sustained Weight Loss and Long-Term Changes in Body Composition and Blood Lipids in Obese Adults. J Nutr. 2009. Mar;139(3):514-21.
3. Arciero, PJ et al. Increased protein intake and meal frequency reduces abdominal fat during energy balance and energy deficit. 2013. Obesity. Vol. 21. 7. 1357-1366.
4. Layman, DK et al. Dietary Protein and Exercise Have Additive Effects on Body Composition during Weight Loss in Adult Women. J Nutr. 2005. Aug;135(8):1903-10.
5. Mettler et al. Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc. 2010. 42: 326-337.
6. Pasiakos, SM et al. Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial. FASEB J. 2013. Sep;27(9):3837-47.
7. Pencharz, PB et al. Recent developments in understanding protein needs - How much and what kind should we eat? Appl Physiol Nutr Metab. 2016 May;41(5):577-809
8. Phillips SM, Van Loon LJ. Dietary protein for athletes: from requirements to optimum adaptation. J Sports Sci. 2011;29 Suppl 1:S29-38.
9. Helms, ER et al. A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. Int J Sport Nutr Exerc Metab. 2014 Apr;24(2):127-38.