Fat Gain Versus Weight Gain: All Calories Are Not Created Equal

In January of this year I read about a new study on how calories from different types of food affect fat gain and weight gain, but until I heard Dr. David Crabb’s discussion of the study on WFIU’s medical program “Sound Medicine” I didn’t appreciate how counter-intuitive and downright strange the results were.  Dr. George Bray of the Pennington Biomedical Research Center in Baton Rouge began by determining the daily caloric needs of 25 healthy men and women.  Then, over an eight-week period, he fed them 1000 calories more.  

The participants were divided into three groups according to the type of diet they were fed during the study.  Some received a diet low in protein - about 5% - and high in fat; others ate a normal protein diet of roughly 15%, an average of 139 grams per day; while the third group consumed a high protein diet of 26%, about 228 grams per day, and very little fat.  Carbohydrate levels for all three groups were the held constant.
   

At the end of the eight weeks all the groups had put on the same amount of fat but weight gains varied among the groups in an unexpected fashion.  The low protein/high fat group put on the least amount of weight and those on the high protein/low fat diet put on the most but the normal and high protein groups gained lean body mass in addition to fat and increased their energy output, while the low protein group actually lost lean body mass.  In his commentary Dr. Crabb notes that it is surprising that the protein in the diet alone produced an increase in lean body mass without any sort of physical training.  (The study did not involve any exercise for any of the participants.)  Presumably the loss of lean body mass would make it harder for the high fat group to lose the weight they had gained once they started to do this, though the study did not address that point.

Some commenters on the research see the study as further evidence of the unreliability of BMI as an index of good health.  At the end of the study the low protein group weighed less but were also less fit.  One aspect of the study seems to confirm a point made by nutrition researcher Douglas Paddon-Jones, that the body does not absorb more than a certain amount of protein, about 30 grams per meal maximum for most people.  Those on the high protein diet did not gain much more lean body mass than those on the normal protein diet.  

Related post:  “Get Older, Stay Strong:  Exciting New Research" 3/08/2012