Researchers put 40 chubby young men on a 4-week diet and exercise program. The diet was very strict. All the subjects consumed about 40 percent fewer calories than they needed to maintain their current weight. They trained with weights and did HIIT (high intensity interval training) six days per week.

While all of them had their calories slashed, half of the subjects were fed more protein than the other half. The lower protein group consumed 1.2 grams per kilogram per day. The higher protein group had 2.4 grams per kilogram per day.

Both groups lost fat. No surprise there. But the higher protein group lost more fat, 10.5 pounds, compared to the lower protein group, who lost an average of 8 pounds. Pretty significant since we're only talking about 4 weeks here. That would be 15 pounds more fat loss over 6 months.

And now it gets really interesting. The group that got to eat more protein built some muscle during the study (about 2.5 pounds). The lower protein group didn't lose any muscle, but didn't add any either.

• You can build muscle and lose fat at the same time. So there.
• When you're dropping calories to lose fat, eat more protein. You'll build some muscle and lose more fat.
• Weight training is absolutely essential for the dieter. Even though one group in the study consumed very low calories and less protein, because they lifted weights they were at least able to keep all their lean body mass and not lose any. Similar studies where dieters didn't weight train showed muscle loss.
• A calorie is not a calorie. The subjects in each group consumed about the same amount, but the higher protein group had better body composition in the end.

1. Longland TM et al. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr. 2016 Mar;103(3):738-46. PubMed.