https://jissn.biomed...970-020-00348-7
Our new paper just pubbed in JISSN shows a keto diet promoted greater fat loss but was suboptimal for increases in lean mass and strength when compared to a protein-equated higher-carb diet in resistance-trained women. Now, before drawing conclusions, it's important to point out some limitations of the study.
Although we made extensive efforts to control calories consumed between conditions, it appears that the keto group ultimately consumed fewer calories than the higher-carb group (perhaps because of satiety factors or perhaps boredom with the diet). If so, it would be expected that fat loss would be greater and that muscle gains would be lower in the keto group. Also, we used DXA to measure body composition, which is sensitive to changes in body water. Given that keto diets cause a reduction in glycogen, and thus a reduction in intracellular water (each gram of glyogen attracts ~3 g of water), the measurement of lean mass may have been influenced by differences in muscle water concentration.
That said, when considering this study in context with the body of literature, a general take home would be that the keto diet is a viable strategy for losing body fat, but would not be ideal if your goals are to maximize strength and hypertrophy. Big kudos to Salvador Vargas Molina for leading the way on this project!
©Brad Shoenfeld.