In humans, some studies demonstrate a link between eating night time snacks and poor health outcomes such as obesity, increased cholesterol, increased blood sugar levels, and increased risk of coronary heart disease. There are several explanations for these observations. First, eating late at night results in reduced fat and carbohydrate metabolism (or breakdown) by the body. Second, there is reduced energy expenditure for night eaters. This may be due to fewer opportunities to burn off calories at night, and hence they tend to put on weight more easily. Third, eating late into the night means reduced hours of sleep, and this increases the “hunger hormones” (ghrelin) and reduces the “satiety/ fullness hormones” (leptin), resulting in overeating and weight gain. Insufficient sleep can also reduce the body’s sensitivity to the hormone insulin and increase inflammation of blood vessels, hence predisposing a person to diabetes and heart problems.
Human trials on night shift workers concur with the above result and show a higher prevalence of overweightness, abdominal obesity, elevated triglycerides, abnormal lipid levels, pre-diabetes, and decreased kidney function, when compared to day-time workers.