Loss of Appetite on Hot Days – Tips and Advice

While it is commonly believed that summer heat waves naturally suppress appetite, scientific evidence supporting this observation remains inconclusive, and the precise biological mechanisms have yet to be definitively identified. As early as 1947, researchers R. E. Johnson and R. M. Kark published findings in the journal *Science* demonstrating statistically significant variations in daily caloric intake among soldiers deployed in drastically different thermal environments—ranging from freezing to tropical conditions. Subsequent investigations led by I. Mandic, involving Canadian soldiers performing daily exercises at 30°C, 21°C, and −10°C, confirmed subjective reports of reduced hunger during heat exposure, correlated with markedly elevated leptin concentrations (an appetite-suppressing hormone) in male participants at 30°C compared to colder settings. Paradoxically, however, despite these hormonal shifts and self-reported decreases in appetite, total daily caloric consumption remained consistent across all three temperature groups. C. P. Herman proposes several theoretical frameworks to explain this phenomenon, including the *thermostatic hypothesis*, which posits that food ingestion generates additional metabolic heat (termed postprandial thermogenesis), thereby exacerbating the body’s thermoregulatory burden under heat stress. Given that approximately 10% of ingested energy is expended on digestive and nutrient absorption processes—which inherently produce heat—the body may instinctively limit food intake to mitigate this effect. An alternative hypothesis advanced by Herman suggests that during summer months, the body’s *weight set point* undergoes recalibration, leading to a physiological drive to maintain a lower body mass in response to thermal stress.