The idea has long been established that eating at night before bed is more fattening than other meals during the day, especially if they are high in carbohydrates or fat. The explanation that is usually given is that, when going to sleep and not doing any activity that uses up the consumed energy, Carbohydrates will be transformed into fat to be stored. Several scientific studies have come to conclusions that contradict these assumptions.
Activity is key, not time of day
The most common explanation for why eating carbs at night makes you fatter than during the day is that your basal metabolism slows down while you sleep. Since there is a lower basal metabolic rate and no extra calorie-burning activity is being performed, the consumed carbohydrates will not be spent and will go directly to the fat stores.
According to a study by Katayose et al, during the first half of sleep the basal metabolic rate is reduced by approximately 35%, but it increases during the second half causing the basal metabolic rate calculated during the entire period of sleep to be approximately the same as the basal waking metabolism. It can therefore be said that there is almost no difference between eating carbohydrates in the morning and going to work in an office sitting for 8 hours and eating carbohydrates in the evening and going to sleep for 8 hours.
In addition to the basal metabolism being similar during sleep and during wakefulness, some studies show that the regular practice of physical exercises can even increase metabolic expenditure during sleep. So, with the available data, the idea that carbohydrates should be avoided before bedtime because metabolism slows down does not hold up as a valid idea.
More attention must be paid to the total calculation of calories consumed and expended throughout the day, since, in any case, the energy consumed and not spent will be stored, first in glycogen stores and, if they are full, it will be transformed into fat . In this sense, it can also be argued that if some physical activity is practiced before dinner, the glycogen stores will have decreased and the consumed carbohydrates will be stored as glycogen and not as fat.
It is also often mentioned that during sleep insulin sensitivity is lower, which means that carbohydrates are not “burned”. In fact, some studies have shown that insulin sensitivity and glucose tolerance are lower in the evening than in the morning, likely due to overnight fasting. However, compared to a midday meal there is no difference. Therefore, this aspect does not seem to be enough to recommend avoiding carbohydrates at night.
Carbs at night can even make you lose weight
In a study conducted in 2011, weight gain was compared over six months between two groups that consumed the same diet but were distributed differently. One group distributed carbohydrates during the day (control group) and another group consumed 80% of carbohydrates during the night (experimental group).
The experimental group ended up losing weight compared to the control group. The researchers explained this phenomenon by the hormonal response generated. In the experimental group, lower baseline values of insulin in the blood were observed, but also higher levels of adinopectin, a hormone synthesized in adipose tissue that produces increased sensitivity to insulin in tissues such as the liver, skeletal muscle and adipose tissue.
This study compares carbohydrate intake distributed during the day and cumulative intake at night. However, before definitively advising that carbohydrates be consumed at night, we would have to wait for more studies that provide more specific data. For example, a comparative study between carbohydrate consumption in the morning, consumption at night and consumption distributed throughout the day would be very interesting.