Higher protein intakes promote fat mass loss
Following a hypoenergetic diet means consuming fewer calories, and in other words, having less calories to turn into energy. During caloric restriction, studies have recommended that resistance training can attenuate the loss of skeletal muscle mass by stimulating muscle protein synthesis.
But according to the researchers, “the role of hormones and their association with body composition under hypoenergetic conditions combined with high-intensity exercise has been less well studied.”
In their paper published in The American Journal of Clinical Nutrition, scientists conducted a single-blind, randomized, parallel-group prospective trial on 40 overweight men (meaning a BMI larger than 25) to see if, during an energy deficit of ~40% compared with estimated energy requirements, eating a higher protein diet is more beneficial for fat mass loss and lean mass gain than lower protein diets.
Diet and supplementation
The group of 40 men were divided into two: 20 men assigned a higher protein diet, and another 20 men assigned a lower protein diet.
Participants were provided all meals and beverages throughout the 28-day observation period, and diets were personalized based on each participant’s requirements (linked to habitual daily activities and body composition).
Both the high protein and low protein control groups received whey protein beverages to be consumed throughout the day and immediately after training in the presence of the investigators on exercise days. The high protein group members’ beverages were altered by adding Agropur IsoChill 9010 Instantized Whey Protein Isolate.
The high protein group was given around 49 g of protein a day in dairy beverage form, compared to 15 g for the control group. Additionally, the high protein group’s beverage had approximately 48 g of carbohydrate a day compared to 41 for the low protein group.
In sum, the high protein group consumed three times the protein recommended daily allowance, while the control group consumed protein close to their habitual consumption but still adjusted to be higher than the recommended daily allowance.
Exercises
Study participants performed a full-body resistance circuit with 10 repetitions for three sets for two days of the week, and a high interval training/sprint interval training for another two days. For the remaining two days, participants completed a plyometric body weight circuit.
“We included forms of exercise that would promote rapid gains in fitness and strength, as well as promotion of lean mass retention,” explained the researchers. “However, we also implemented post-exercise provision of a predominantly whey protein supplement to augment lean mass preservation in the face of a marked 40% energy deficit.”
“It is also worth noting that our training program involved intense high-volume resistance exercise and HIT/SIT, which has not, to our knowledge, been studied in such a severe energy deficit previously,” they added.
Seeing results
The researchers found that the group with higher protein intake during a period of marked energy deficit resulted in an increase of lean body mass and greater loss of fat mass compared to the lower protein control group.
But on the latter group, the researchers noted that “lean body mass was unchanged during a period of high-intensity exercise training and substantial energy deficit even when the amount of protein consumed was lower.”
“Despite differences in body composition changes between groups, and in contrast to our hypothesis, there were no differential responses in strength, performance, aerobic fitness, or anaerobic power between groups in response to the intervention,” they added.
The researchers contend that, given their data, “protein dose per meal, protein quality, and timing of consumption relative to exercise would become more important in determining changes in lean body mass when in a caloric deficit because it decreases in basal rates of muscle protein synthesis and a reduced sensitivity of muscle protein synthesis to protein feeding.”
