Appetite and weight gain suppression effects of alcohol depend on the route and pattern of administration in Long Evans rats

Ethanol can be a food source but its effects on energy balance and contribution to obesity remain inconclusive. In this study, we hypothesized that the effects of ethanol on energy intake and body weight would depend on the administration dose, pattern and the blood ethanol concentration (BEC) time-course. Experiment 1 examined changes in food intake, diet preference, and body weight after saline or ethanol (1 and 3 g/kg) injection (IP). Experiment 2 compared the effects in rats that received either 3 g/kg/day ethanol administered all at once (EtOH_S) or 2 1.5 g/kg injections spaced by 3 h (EtOH_D). Experiment 3 examined the effects of 7.5 h/day, Mon through Fri for 8 weeks, voluntary ethanol drinking (5% and 10% ethanol) on food intake and body weight. Results of Experiments 1 and 2 indicate that acute ethanol administrations dose-dependently reduced energy intake, high fat diet preference and weight gain. Acute 3 g/kg ethanol injection in the EtOH_S group decreased energy intake, weight gain and visceral fat to a greater extent than in the EtOH_D group. Results of Experiment 3 show that male and female rats voluntarily drank 1.65–2.31 g/kg ethanol within 3.5 h with reduced chow intake but unchanged total energy intake and weight gain. Furthermore, 3 g/kg ethanol injection resulted in BEC that remained at intoxicating levels e.g. > 120 mg/dL for several hours post-administration and was higher in the EtOH_S than in the EtOH_D group. In contrast, BEC in voluntarily drinking was ~ 67 mg/dL and decreased to below 10 mg/dL 5 h after termination of ethanol access. Taken together, these data suggest that 3 g/kg ethanol injection robustly suppresses appetite and weight gain due to the higher BECs attained. Furthermore, BEC attained and maintained is a determining factor for how ethanol administration affects appetite and long-term energy balance.