Macronutrient disposal during controlled overfeeding with glucose, fructose, sucrose, or fat in lean and obese women

Background: Previous short-term studies (less than or equal to 6 h) showed differences in energy expenditure (EE) and macronutrient oxidation in respo nse to overfeeding with different types of dietary carbohydrate. This findi ng could have implications for obesity. Objective: We used 96-h continuous whole-body calorimetry in 8 lean and 5 o bese women to assess metabolic disposal (energy dissipation and glycogen or fat storage) of a controlled excess of dietary energy supplied as differen t carbohydrate sources or as fat. Design: Five dietary treatments were applied in random order: energy balanc e (control) and overfeeding by 50% of energy requirements with fat (O-fat) or predominantly with glucose, fructose, or sucrose (O-cho). Macronutrient oxidation rates were assessed from nonprotein gaseous exchanges. Net macron utrient balances were calculated as cumulative differences between intake a nd oxidation, Results: Increased EE in response to overfeeding dissipated 7.9% of the ene rgy excess with a variation in EE of <1.7% across over feeding treatments ( NS), EE during the O-fat treatment significantly exceeded that during the c ontrol treatment in the lean but not in the obese women. There were no sign ificant differences between lean and obese women in macronutrient oxidation or balances, so data were pooled. O-cho induced glycogen storage on day 1 (approximate to 100 g) but thereafter progressively stimulated carbohydrate oxidation so that balance was reached on days 3 and 4. Fat oxidation was p roportionately suppressed. Of the excess carbohydrate, 74% was oxidized; th ere were no significant differences between the various O-cho treatments. O -fat stimulated fat oxidation by 18% and suppressed carbohydrate oxidation. On average, 12% of the excess energy was stored as glycogen and 88% as fat ; there was no significant difference between overfeeding treatments. Conclusion: There was no significant difference in fat balance during contr olled overfeeding with fat, fructose, glucose, or sucrose.