Abstract P471: Increased Salt Intake Reduces Diet-induced Thermogenesis in Healthy Men

Abstract

Objective: High salt intake is a potential risk factor for obesity independent of energy intake, though underlying mechanisms remain unclear. Excessive body fat accumulation is caused by a positive energy balance over an extended period of time. Food intake causes a postprandial increase in energy expenditure. This postprandial effect represents approximately 10% of the total energy ingested over 24h. A decrease in diet-induced thermogenesis (DIT) contributes to a positive energy balance and weight gain over time. The present study investigated the effect of a 14-day high salt intake on DIT in healthy men. Methods: We enrolled eight healthy men (34 ± 7 years, BMI 24 ± 2 kg/m 2 ) in an exploratory, longitudinal study (Clincaltrials.gov identifier: NCT02509962). Probands received 6 g salt daily using sodium chloride tablets (Slow Sodium tablets, HK Pharma Ltd.) over 14 days on top of their habitual diet. Measurements were taken at baseline (V1), on day 3 (V2) and day 14 (V3) during and on day 9 (V4) after the salt challenge, respectively. At these time points, nocturnal ambulatory blood pressure monitoring, bioelectrical impedance analysis (BIA), food intake from 3-day food records, and resting and postprandial energy expenditure were obtained. Energy expenditure was measured by indirect calorimetry in a respiratory chamber after a 12h overnight fast and a standardized 440 kcal, high-protein meal. Results: Nocturnal systolic blood pressure increased after salt challenge (V1: 105.8 ± 8.5, V3: 111.2 ± 9.1 mmHg, P = 0.02). There was a trend towards higher energy intakes (V1: 2296 ± 752 kcal, V3: 2866 ± 831 kcal, P = 0.1). However, DIT was significantly decreased at all time points during and after salt challenge compared to baseline (V1: 17.3 ± 2.7%; V2: 11.3 ± 2.3%, P = 0.01; V3: 10.7 ± 3.6 %, P = 0.03; V4: 14.4 ± 2.5%, P = 0.04; all vs. V1). After 14 days of high salt, subjects expended 30 kcal less for metabolic processes after meal challenge. Assuming a total energy intake of 2300 kcal/d, this accounts for a 150 kcal positive energy balance. Conclusion: A moderate short-term increase of salt intake decreased the thermic effect of a high-protein meal. This could contribute to the observed weight gain in populations consuming a Western diet high in salt.