Factors associated with body weight gain and insulin-resistance: a longitudinal study

BACKGROUND: Obesity results when energy intake (EI) chronically exceeds energy expenditure, but the role of metabolic factors, including insulin resistance, remains unclear. This study longitudinally investigated factors associated with changes in body weight. SUBJECTS: A cohort of 707 adults without diabetes were investigated at the 4-year follow-up visit. Habitual intake of energy and macronutrients during the past 12 months was assessed using a validated Food Frequency Questionnaire for the local population. Homeostatic model assessment of β-cell function and insulin resistance (HOMA-IR) was used as a surrogate measure of insulin resistance. Additionally, PNPLA3 was genotyped. RESULTS: Eighty-seven participants were weight gainers (G; cutoff value = 5 kg), and 620 were non-gainers (NG). Initial anthropometric and diet characteristics, as well as insulin concentrations and HOMA-IR values, were similar in both groups. Four years later, G showed significantly increased EI, insulin concentrations, and HOMA-IR values. G had a higher prevalence of the PNPLA3 CG and GG alleles than NG (P < 0.05). The presence of G was independently associated with age (OR = 1.031), EI change (OR = 2.257), and unfavorable alleles of PNPLA3 (OR = 1.700). Final body mass index, waist circumference, and EI were independently associated with final HOMA-IR (P < 0.001). CONCLUSIONS: EI is associated with body weight gain, and genetic factors may influence the energy balance. Insulin resistance is a consequence of weight gain, suggesting a possible intracellular protective mechanism against substrate overflow. CLINICAL TRIAL REGISTRATION: ISRCTN15840340.