RESUMEN
BACKGROUND & AIMS: Time-restricted feeding (TRF) studies usually are of short-term, involving heterogeneous populations, without a control group with similar energy restriction. Besides, it seldom assess vital signs such as body temperature and heart rate, which may be influenced by the fasting state. In this investigation, we assessed the long-term effects of TRF on body weight, body composition and vital signs of low-income women with obesity undergoing diets with the same energy deficit. METHODS: Low-income women with obesity were randomly allocated to a group with a hypoenergetic diet and 12 h of TRF or to a group with only a hypoenergetic diet, for 12 months. Body fat and waist circumference were estimated using a tetrapolar electrical bioimpedance and an inelastic measuring tape, respectively, at baseline and after 4, 6 and 12 months of intervention. Systolic and diastolic blood pressure, heart rate, and axillary temperature were measured at baseline and 12 months of intervention. The energy content of the diets was determined based on the women's resting metabolic rate (by indirect calorimetry) and level of physical activity (by triaxial accelerometers). Effects were analyzed using an intention-to-treat approach. RESULTS: Fifty-eight women were randomized and 31 (53.44%) were lost to follow-up at 12 months. Dropout rates were similar between groups. In the intention-to-treat analysis, there were no significant changes in the body weight after 12 months (Differences in changes from baseline between groups: -0.05 95%CI [-2.34; 2.24] Kg; p = 0.96). An increase in axillary temperature (0.40 °C, 95% CI [-0.14; 0.67]°C, p < 0.01), a reduction in the percentage of body fat (-1.64%, 95% CI [-3.08; -0.19]%, p = 0.02) and waist circumference (-2.57 cm, 95% CI [-5.73; 0.58] cm, p = 0.03 in the mixed model involving 4 measurements) were observed in the intervention group, when compared to the control group. CONCLUSIONS: TRF showed no effects on weight loss. Nevertheless the findings on waist circumference and body fat, although not clinically meaningful, suggest that this strategy may help in the long-term management of obesity in this population, since it is an easy to apply intervention. Axillary temperature findings warrants further investigation. Registered under www.ensaiosclinicos.gov.br Identifier no. RBR-387v6v. TRIAL REGISTRATION: http://www.ensaiosclinicos.gov.br/rg/RBR-387v6v/.
