Mice eating a low-protein, high-carbohydrate (LPHC) diet had similar improvements in blood glucose, insulin, lipids, and insulin resistance to mice whose calories were restricted. Yet the low-protein mice could eat as much as they wanted and indeed ate a lot more than the caloric-restricted mice.
Dietary Protein to Carbohydrate Ratio and Caloric Restriction: Comparing Metabolic Outcomes In Mice, Cell Reports, 16 June 2015
Summary: Both caloric restriction (CR) and low-protein, high-carbohydrate (LPHC) ad-libitum-fed diets increase lifespan and improve metabolic parameters such as insulin, glucose, and blood lipids. Severe CR, however, is unsustainable for most people; therefore, it is important to determine whether manipulating macronutrient ratios in ad-libitum-fed conditions can generate similar health outcomes. We present the results of a short-term (8 week) dietary manipulation on metabolic outcomes in mice. We compared three diets varying in protein to carbohydrate ratio under both CR and ad libitum conditions. Ad libitum LPHC diets delivered similar benefits to CR in terms of levels of insulin, glucose, lipids, and HOMA, despite increased energy intake. CR on LPHC diets did not provide additional benefits relative to ad libitum LPHC. We show that LPHC* diets under ad-libitum-fed conditions generate the metabolic benefits of CR without a 40% reduction in total caloric intake.
*LPHC: 5% protein, MPMC: 33% protein, HPLC: 60% protein
Note that restricting the calories of the low-protein, high-carb mice did not provide additional benefit.
They tested six diets, three levels of protein and a caloric restriction (CR) or ad-libitum (AL) arm for each. The charts in this study are something else. Look at this one, specifically the bottom row, C. The AL LPHC mice had the lowest body fat, lower than any of the CR mice!
From their literature review:
Low protein intake has also been associated with better health and reduced mortality in observational studies of humans (Levine et al., 2014), while high-protein, low-carbohydrate (HPLC) diets are associated with higher mortality, cardiovascular disease, and diabetes mellitus (Fontana and Partridge, 2015; Fung et al., 2010; Lagiouet al., 2012; Simpson et al., 2015).
The low-protein, high-carb mice ate the most, had the lowest body fat, and the most energy. Beat that!