When weight is lost through caloric restriction, a higher protein intake is usually seen as a good idea due to preserving lean mass during the weight loss period.
A study that stratified gender found that a 500kcal dietary restriction for one year resulted in 9.9-11.2% weight loss in overweight persons with no difference between gender and overall weight lost did not differ between the high protein group (1.6g/kg) and the low protein group (0.8g/kg); when measuring only fat mass, the high protein group lost significantly more fat (14.3 ± 11.8%) than did the low protein group (9.3 ± 11.1%) when calories were kept equal. This study found that higher protein benefited both men and women, although men inherently lost more weight as a percentage of body fat.
Protein and weight loss is also important for postmenopausal women and older men, as caloric restriction-induced weight loss appears to inherently reduce lean mass, with more lean mass being lost when dietary protein is lower despite caloric deficit being similar. When investigating older (65.2 ± 4.6) women who are either overweight or obese and given a diet consisting of 1,400 calories (with a set amount of calories from each type of macronutrient) the addition of 50g whey protein twice a day to this calorically restricted diet induced more weight loss (-8.0% ± 6.2%) than did adding 50g carbohydrate (-4.1% ± 3.6%) despite calories being the same. The protein group lost slightly more muscle as an overall percentage secondary to weight loss, but gained when measured relative to body fat losses. Another study comparing 15% protein (in relation to overall calories) against 30% protein found that the low protein group lost more weight (11.4 +/- 3.8kg) with 37.5% of it being lean mass, while the higher protein group had a slightly lesser rate of weight loss (8.4 +/- 4.5kg) with approximately half as much lean mass lost (17.3%). These results are repeated in various trials with similar results, with higher protein reducing losses in lean mass associated with diet regardless of source. Even a small trend towards greater consumption of protein and dairy foods is associated with more favorable body composition changes during weight loss in the older population.
Consumption of protein in the higher range, usually seen as around 1g/lb of lean mass (if you know your body fat percentage and can calculate lean mass) or 25-30% overall calories, is more protective of lean mass during periods of intentional weight loss when calories are controlled for
One study conducted over 12 weeks comparing low (1.1g/kg) against high protein (2.2g/kg) found that the high protein group not only lost more body fat mass (with no significant differences in overall weight, due to muscle retention) but the high protein group also experienced a reduction in LDL cholesterol and total cholesterol not seen in the low protein group. A high protein diet (34% of calories) against a high carbohydrate diet (17% protein) also appears to be more effective at reducing triglycerides, and is seemingly more effective for both health and body fat reduction in those obese persons with high baseline triglycerides.
The above studies tend to control for overall protein intake, rather than sources. They can be used to argue that protein per se helps with fat loss and muscle preservation with little to no difference when comparing one source to another.
When looking at the quality of protein sources in other studies, those that tend to have a higher percentage of essential amino acids tend to be more well correlated to inducing fat loss; this appears to extend to bone health as well. These sources tend to be animal sources; meat, fish, eggs and dairy. It should be noted that the protein supplements of whey and casein are two common protein supplements and are both derived from dairy (specifically, dairy protein is about 80% casein to 20% whey).
Overall, protein per se takes precedence. Beyond that, animal sources tend to be better than plant sources due to a higher percentage of essential amino acids
For a more detailed analysis, see our article on ideal levels of protein consumption based on your goals.
- Fact check: does glutamine build muscle?
- How can you assess protein quality?
- Whey Protein and Efficiency
- What should you eat for weight loss?
- Is semen high in protein?
- High-Protein Diets Linked to Cancer: Should You Be Concerned?
- Can eating too much protein be bad for you?
- Are there health benefits to a low carb diet?
- 5 little-known facts about protein
- How much protein do you need after exercise?
- Should one gram per pound be the new RDA for bodybuilders?
- How much protein do you need per day?
- Does high-protein intake help when dieting?
- Whey vs soy protein: which is better when losing weight?
- How to minimize fat gain during the holidays
- How much protein can you eat in one sitting?
- Do muscle building supplements cause testicular cancer?
- Why do my muscles get sore?
- Why you shouldn't be always taking antioxidants, especially if you want to build muscle
- Does dark chocolate’s epicatechin content promote muscle growth?
- Does ashwagandha increase testosterone?
- Can arachidonic acid work as a bodybuilding supplement?
- Will lifting weights convert my fat into muscle?
- Does Garcinia Cambogia help with weight loss?
- Can hypothyroidism lead to fat gain?
- How do I stay out of "starvation mode?"
- Measuring body fat percentage: It's an accuracy thing
- Does eating at night make it more likely to gain weight?
- Does diet soda inhibit fat loss?
- How to minimize fat gain when you binge
- A compound from beer may help fat loss
- Can one binge make you fat?
- Will carbs make me fat?
- How do I get a six-pack?
- How do I lose fat around my belly?
- Does eating fat make you fat?
- Is diet soda bad for you?
- How important is sleep?
- I have lost significant weight and now have loose skin. How can I tighten up my skin?
- Low-fat vs low-carb? Major study concludes: it doesn’t matter for weight loss
- Does aspartame increase appetite?
- Is my “slow metabolism” stalling my weight loss?
- The lowdown on intermittent fasting
- I'm not too tired to stuff my face
- Will eating breakfast keep you lean?
- Do you need to detox?
- Is it really that bad to skip breakfast?
- Will my breasts shrink with weight loss?
- Effects of protein intake and gender on body composition changes: a randomized clinical weight loss trial. Nutr Metab (Lond). (2012) Evans EM, et al.
- Lean mass loss is associated with low protein intake during dietary-induced weight loss in postmenopausal women. J Am Diet Assoc. (2008) Bopp MJ, et al.
- The effects of a higher protein intake during energy restriction on changes in body composition and physical function in older women. J Gerontol A Biol Sci Med Sci. (2011) Mojtahedi MC, et al.
- Effects of dietary protein on the composition of weight loss in post-menopausal women. J Nutr Health Aging. (2008) Gordon MM, et al.
- A controlled trial of protein enrichment of meal replacements for weight reduction with retention of lean body mass. Nutr J. (2008) Treyzon L, et al.
- Effect of an energy-restricted, high-protein, low-fat diet relative to a conventional high-carbohydrate, low-fat diet on weight loss, body composition, nutritional status, and markers of cardiovascular health in obese women. Am J Clin Nutr. (2005) Noakes M, et al.
- High protein diets decrease total and abdominal fat and improve CVD risk profile in overweight and obese men and women with elevated triacylglycerol. Nutr Metab Cardiovasc Dis. (2009) Clifton PM, Bastiaans K, Keogh JB.
- Increased consumption of dairy foods and protein during diet- and exercise-induced weight loss promotes fat mass loss and lean mass gain in overweight and obese premenopausal women. J Nutr. (2011) Josse AR, et al.
- Effects of protein vs. carbohydrate-rich diets on fuel utilisation in obese women during weight loss. Forum Nutr. (2003) Labayen I, et al.
- Effects of 4 weight-loss diets differing in fat, protein, and carbohydrate on fat mass, lean mass, visceral adipose tissue, and hepatic fat: results from the POUNDS LOST trial. Am J Clin Nutr. (2012) de Souza RJ, et al.
- Quality protein intake is inversely related with abdominal fat. Nutr Metab (Lond). (2012) Loenneke JP, et al.
- Short report: Relationship between quality protein, lean mass and bone health. Ann Nutr Metab. (2010) Loenneke JP, et al.