Calorie Burning While You Sleep

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There are common misunderstandings about the amount of calories consumed at various times of day and their relation to calorie burning during sleep. Below is updated information, to help you sort fact from fiction. By clarifying how calorie burning really works, it is easier to determine the implications of eating just before sleeping.

False assumptions about calorie burning

A common assumption is that humans burn more calories when we are awake for longer periods, but that is not the case. The metabolism (metabolic rate) becomes down-regulated when people sleep less. That means that when your sleep is reduced, your body preserves energy by slowing the rate at which it is burning calories. The body seeks to meet its increased metabolic needs resulting from keeping longer hours doing waking activities by gearing down in order to burn less fewer calories.

How calorie burning really works

Metabolism is the biochemical process in which the calories you consume are converted to energy for your body to use for passive functions during sleep and waking hours, including breathing, heart beat to circulate blood, growing new cells, repairing existing cells, and making adjustments of hormone levels. Your metabolism, plus these additional factors, all together determine your body’s daily calorie usage:

  • Food processing (thermogenesis): Digesting food, absorbing it, transporting, and storing it takes a certain amount of calorie per day. Generally, the body’s energy needs for processing food remains stable and doesn’t easily change.
  • Physical activity and exercise: such as playing sports, walking around your workplace, cleaning house, etc., account for most of your daily calorie burning. The amount of calorie burned by physical activity can vary widely from day to day.
  • Environmental impactors: Effects on your lifestyle, including:
    • Sleep
    • Physical activity
    • Stress levels
    • Eating habits
  • Height and bone structure: Larger or more muscular people burn more calories, even while resting.
  • Sex: Men typically have more muscle and less body fat than women of the same weight and age, which means the men burn more calories around the clock.
  • Age: As people age, our muscle (which burns calorie) is likely to decrease, and fat (which does not burn calorie) eventually is at a higher percentage of your total body weight. That means the body’s calorie burning slows down.

These factors all combine to result either in a balance or imbalance in the equation of your energy intake to output. In other words, if you take in a greater or smaller number of calories than you burn, you will gain or lose weight accordingly.

Eating before sleeping and weight gain

Weight gain can only occur due to consuming more calories than the body burns. A pound of fat contains 3,500 calories. Consuming 3,500 calories more than the body burns results in a one-pound weight gain. This is regardless of what time of day the calories are consumed.

However, while sleep cannot cause weight gain, eating just before going to sleep can result in weight gain. Although scientists have not yet identifies the specific reason why, it appears that the typical sources of late-night calories consumed and sleep issues due to late eating are the two most likely causes.

  • Sources of late-night calories: Late-night eating may tend to involve less healthy food, food more typically eaten at mealtimes, and may be instead snack foods with empty calories and high fat and calorie content.
  • Sleep issues: Research indicates that eating before going to bed can impact sleep quality, causing disruptions of normal sleep cycles and interfere with natural processes involved in maintenance of body weight.For example, insulin (hormone that conveys blood sugar to cells for use as fuel) functions with the body’s circadian clock (which lets your body know it’s time to sleep and fast (not eat). At night, because the body expects to be sleeping, cells naturally resist the hormone. Blood sugar levels rise, and eventually fat accumulates. In extreme cases, Type 2 diabetes can result.

Take Away Message

Ultimately, although your body’s basic energy needs (metabolism) is more or less consistent over time and not easily changed, regulating physical activity and eating habits are central to managing the balance of calorie intake to expenditure. And, as the relationship between late eating, sleep, and the body’s natural regulation of calorie usage, it appears that a wise approach to managing the balance is to avoid eating near bedtime, or to eat very lightly during that period.