High Protein Diets and Body Composition
Does an increase in protein lead to fat gain?
Written by: Joachim Bartoll, September, 2015
Classic Muscle Newsletter, Oct 2015
High protein diets have been popular for many years within the fitness and bodybuilding community. One of the reasons are quite obvious: the majority of competing athletes use anabolic steroids, which increases protein synthesis around the clock and let our body use more protein for cell repair and growth. Their physiology is temporarily “enhanced”, so extra protein is beneficial. But what about the natural weight lifter?
The common recommendation for physically active and resistance training individuals are usually a daily intake between 1.4 to 2.0 g of protein per kilogram of body weight. When the goal is muscle growth, the most common recommendation is about 2.3 g of protein per kg. However, a lot of athletes and coaches swears by a much higher protein intake than that, especially on a fat cutting/competition diet. Many going as high as 3 g/kg a day or more.
The critics however, usually say that a high protein diet is tough on the kidneys, can lead to bone mass loss, dehydration and even increased body fat. Their reasoning for the latter is that since a gram of protein contains 4 calories, if the ingestion of any calories, including protein, exceeds daily activity levels, your body will convert the excess calories into fat. This calorie is a calorie dogma may seem sensible at first glance, but is it really?
Can you get fat from consuming too much protein?
The reality is that it's very difficult to get fat from eating too much protein. It's not impossible, just not likely. Although all macronutrients contain calories, the metabolic effect and hormonal responses differs. Excess protein that is consumed is first degraded, then oxidized in the liver. The nitrogen portion that makes protein uniquely different from carbohydrates and fat, is first converted into ammonia, then into urea. The urea is then sent to the kidneys and is subsequently excreted from the body. This differs hugely from the metabolism of fat and carbohydrates. When excess fat is ingested with excess carbohydrates, the ingested fat is rapidly converted into body fat or triglycerides. The same holds true for carbohydrates. The primary storage site for carbs in the body is in the form of liver and muscle glycogen. As long as these glycogen stores aren't filled, the likelihood of carbohydrates being converted into body fat is low. However, ingesting processed/fast acting carbohydrates tend to boost insulin levels to a high degree, and that in itself inhibits the use of fat as an energy source, as well as it seems to maintain existing fat stores.
So ingesting fast acting sources of carbohydrates, or sources like fructose that primarily fills liver glycogen, will make it harder to lose excess body fat; as the scenario changes when any type of carbohydrate are ingested once the glycogen stores in liver and muscles are filled. When that happens, any excess carbohydrates that are ingested in excess of energy use is also rapidly converted to a type of fatty acid called palmitic acid, which is a saturated fat that is easily stored in the body.
Keeping these basic facts in mind, protein simply seems to be the least likely macronutrient to promote body fat accretion.
What does the science say?
One study published a few years ago compared high and low protein diets, as well as low fat diets in sedentary subjects. The researchers found that while any diet is capable of increasing body fat levels when excessive calories in relation to activity is ingested, the highest protein diet not only produced the least amount of body fat, but also resulted in reduced body fat in the subjects. Since the people in this study didn't exercise, the results would probably have been even more favorable if they would have been more active, preferable by lifting weights. That assumption takes us to another study.
Last year, a study was published that examined the body composition effects of consuming a very high protein diet in resistance-trained individuals. The high-protein group ingested 4.4 grams of protein per kilogram of body weight for 8 weeks. That’s more than double the amount of protein that is usually recommended for muscle building purposes. The high-protein group consumed on average 307 ± 69 grams of protein compared to 138 ± 42 grams of protein in the control group.
The high-protein group where then instructed to maintain the same intake of fat and carbohydrates that they have been consuming previous to the study. In other words, they simply added (more than doubled) their current intake of protein without changing anything else – adding more than 600 kcal to their daily total calorie intake. Despite this, the study showed that none of the trainees consuming a higher protein intake exhibited any evidence of increased body fat synthesis. Again, because of their regular weight training exercise, any excess protein they consumed was oxidized in the liver.
In late September this year, the authors of the above study released a follow-up. This time, their study consisted of 48 healthy, resistance-trained men and women who were divided into a normal-protein group or a high-protein group. Those in the normal-protein group ingested 2.3 grams of protein per kilogram of body weight, which is the amount suggested by many as ideal for promoting muscle growth. The high-protein group consumed 3.4 grams of protein per kilogram of body weight, less than the original study, but still higher than the usual recommended amount. During the study, all subjects trained using a split workout routine that involved training different muscles on various days.
The results showed that those in the high-protein group showed gains in body weight (-0.7 ± 4.0 kg vs. 1.3 ± 1.3 kg), decreased body fat (-1.7 ± 2.3 kg vs. -0.3 ± 2.2 kg), and percentage of body fat (-2.4 ± 2.9 kg vs. -0.7 ± 2.8 kg). Both groups showed gains in strength and power as judged by standard exercise testing, along with maximal lifts in the bench press and squat exercises. No adverse health changes occurred in either group. This study adds to the large body of literature showing that consuming a higher protein diet while engaged in exercise (especially resistance training) does not cause any adverse health effects, nor does it promote an increase in body fat levels. In actuality, consuming a higher protein intake while engaging in resistance training tends to promote a decrease in body fat, even when consuming slightly more calories than usual.
One of the most common ways to repair and increase one’s metabolism after a severe fat loss diet is to slowly add in carbohydrates every week, or every other week. This is usually how I manage fat loss diets as well, adding in carbohydrates and sometimes extra protein as the diet progresses. This can be in steps of 50 to 150 kcal, depending on muscle mass and perceived insulin sensitivity.
With the research above in mind, it could actually be even more beneficial to add in extra protein periodically during a fat loss diet. This will both act as an anti-catabolic precaution and a way to increase your metabolism – especially if you know you’re insulin resistant. The same will probably hold true during a muscle gain diet. I’ve always added in both carbohydrates and protein at even intervals when gaining muscle. It could also be used to shift your macronutrient ratios. If you feel you’re gaining to much fat in your pursuit of new muscle mass, simply maintain your energy intake, but shift your macros to more protein and less carbohydrates and/or fat.