Metabolic status in growing rats fed isocaloric diets with increased carbohydrate-to-fat ratio.
OBJECTIVE
A low-fat diet is hypothesized to be associated with significant weight loss. However, most previous studies have been limited to low-fat, low-calorie restrictive diets. This study evaluated the effect of isocaloric diets given "ad libitum" but different in relative amounts of fat and carbohydrate on body size, energy metabolism, body composition, insulin-like growth factor-1, and leptin serum levels in growing Wistar rats.


METHODS
Weanling male rats were fed with one of three diets that contained a ratio of carbohydrate to fat of 1:1, 2:1, or 3:1. Food intake, body weight, body length, oxygen consumption, and body composition were measured at ages 21 to 50 d. Serum levels of insulin-like growth factor-1 and leptin were also determined.


RESULTS
Energy intake was similar across groups. The ratio of body weight to body length remained adequate throughout the experimental period. However, groups that received 3:1 and 2:1 showed increased weight and progressive decreases in energy expenditure, body fat composition, and serum level of leptin, but the ratio of insulin-like growth factor-1 to body length was not affected.


CONCLUSIONS
Dietary substitution of fat with carbohydrates contributes to weight gain by decreasing energy expenditure and possibly by decreasing leptin secretion.
Gamba
Carlota A
CA
Department of Biochemistry, Faculty of Dentistry, University of Buenos Aires, Buenos Aires, Argentina.
Friedman
Silvia M
SM
Rodriguez
Patricia N
PN
Macri
Elisa V
EV
Vacas
Maria I
MI
Lifshitz
Fima
F
D000818:Animals; D001823:Body Composition / Q000187:drug effects* / Q000502:physiology; D018752:Diet, Fat-Restricted; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage* / Q000378:metabolism; D002149:Energy Intake / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology; D020738:Leptin / Q000378:metabolism; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D015430:Weight Gain / Q000187:drug effects* / Q000502:physiology
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D020738:Leptin