The results of many recent studies continue to mount in favor of high-protein diets and supplemental protein, both for health and athletics. A recent study in the Journal of Applied Physiology was no exception.
About the Study
The study was designed to answer the following questions:
- Will following a diet that stays roughly the same from a calorie standpoint, but has an average of 33 more grams of protein per day make a big difference without any planned resistance exercise?
- Does it matter whether a high protein intake comes from food sources or supplements?
- What differences result from following more or less the same dietary plan, but with two differently structured workout programs?
The researchers recruited 57 men and women in their late forties and early fifties. None of the subjects were engaged in a regular training program prior to the study. They were divided into three groups, and each group consumed sixty grams of protein divided out into three equal portions throughout the day. Otherwise, all the participants were allowed to eat as they would usually eat.
Two of the groups followed workout plans. One group did a basic weight lifting routine four times per week, with two upper body workouts and two lower body sessions. They did a few sets of basic exercises for ten to twelve reps. The other resistance training group completed a more complex program that included two days of whole-body weight lifting, one day of interval training, and one day of stretching.
The group without the workout plan actually burned the most calories through physical activity on a daily basis, even before the study. That level increased further over the course of the study, so it’s not as if they weren’t moving around, but they weren’t engaged in a structured workout plan. Aside from that increase in energy expenditure they did things pretty much as before, along with the addition of protein.
Effects on Satiety and Caloric Expenditure
Although the protein shakes didn’t reduce the hunger of the participants, there were some mild differences in the high-protein diet. Total calories more or less stayed the same, which indicates that with all that added protein, something went uneaten. To some extent in each group, food-based protein intake did decline. One group also dropped fat significantly.
Effects on Weight Loss, Body Composition, and Insulin Resistance
Each of the groups lost a modest amount of weight, averaging from a couple pounds to over seven pounds. Oddly, although the percentage of bodyweight as lean mass increased, the total lean mass actually decreased. Since these fluctuations were small, I’d guess that the resistance-trained participants did actually gain a small amount of muscle, but lost some water that would be factored into the lean mass.
Insulin resistance also improved when the protein and exercise were combined, and as a result, fasting glucose decreased in the exercise groups. That means the participants who combined exercise and protein intake got healthier.
So even when calories remain the same, a higher protein intake shows health benefits. With the ever-loosening grip of the food pyramid paradigm and increased interest in diets like paleo, there will continue to be more research like this. I suspect it will continue to show that high-protein diets work well for virtually everyone, athlete and non-athlete alike.
References:
1. Paul Arciero, et. al., “Timed-daily ingestion of whey protein and exercise training reduces visceral adipose tissue mass and improves insulin resistance: the PRISE study,” Journal of Applied Physiology 117:1-10, 2014.
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