Introduction: Many obese adults and adolescents undergo repeated cycles of diet-induced weight loss and gain, i.e. weight cycling (WC) or 'yo-yo dieting'. Younger children also show concerns about their body image, as rates of childhood obesity reach alarming proportions in many countries. Epidemiological and experimental studies suggest that WC may increase cardiovascular morbidity/mortality through metabolic disturbances and hypertension. Obesity also increases the risk of renal disease. Thus, we evaluated the consequences of
WC on renal, metabolic and cardiovascular parameters in young rats.
Methods: Experiments were performed in 24 male 6-12 weeks-old Sprague Dawley rats fed with normal chow (4.5% fat) for 24 days. Control group I received a fixed amount of 21 g/d. Cycling group II received the same total amount given as 3 cycles (4 d _33%¼14 g/d, 4 d þ33%¼28 g/d). After a 4-d stabilization period at 21 g/d, all animals were switched for 14 days to 20 g/d of a high fat diet (23.6% fat), isocaloric to 28 g of normal chow. Body weight was measured daily. Blood was sampled every 4 d to analyze plasma glucose,
insulin, creatinine, urea, triglycerides, HDL, LDL and total cholesterol.
Results: Despite similar final body weight (422 vs 424 g in I and II), total body fat was increased in cycling rats (55.3±1.6 vs 60.4±1.8 g, Po0.05). Food cycling was associated with significant under- and overshoots below and above control values for all parameters.
Conclusions: Our data suggest thatWC, without excess food intake or weight gain, may predispose to cardiovascular diseases by promoting fat accumulation. Under/ overshoots occur during WC, putting an additional load on the cardiovascular and renal systems. Repeated glomerular hyperfiltration and hyperlipidemia may induce glomerular sclerosis and nephron loss that may eventually translate into systemic hypertension. Additional fluctuations of plasma glucose, cholesterol and triglycerides may contribute with time to vascular damage, thereby exacerbating hypertension and leading to the development of metabolic syndrome and early-onset diabetes