Sleep is like nutrition for the brain. Most people need between 7 and 9 hours each night. Not sleeping enough—less than seven hours of sleep per night—can reduce and undo the benefits of dieting.

HORMONES 

1. LEPTIN & GHRELIN

Hunger is controlled by two hormones: leptin and ghrelin.

People who are sleep-deprived report having an increased appetite.

The more ghrelin you produce, the more you stimulate hunger while also reducing the amount of calories you burn (your metabolism) and increasing the amount fat you store.

Leptin is a hormone released from fat cells. It suppresses hunger and signals fullness in the brain.When you do not get adequate sleep, the body makes more ghrelin and less leptin, leaving you hungry and increasing your appetite.

You need to control leptin and ghrelin to successfully lose weight.

Sleeping less than six hours triggers the area of your brain that increases your need for food while also depressing leptin and stimulating ghrelin.

2. CORTISOL

When you don’t sleep enough, your cortisol levels rise. This is the stress hormone that is frequently associated with fat gain. It also activates reward centers in your brain that make you want food. At the same time, the loss of sleep causes your body to produce more ghrelin. A combination of high ghrelin and cortisol shut down the areas of your brain that leave you feeling satisfied after a meal, meaning you feel hungry all the time.

3. INSULIN

Insulin is a hormone that moves sugar from the bloodstream into your body's cells to be used as energy.

When cells become insulin resistant, more sugar remains in the bloodstream and the body produces more insulin to compensate.

The excess insulin makes you hungrier and tells the body to store more calories as fat. Insulin resistance is a precursor for both type 2 diabetes and weight gain.

Poor sleep can trigger the body to make more insulin and cortisol. 

Higher insulin and cortisol levels appear to prompt the body to store energy as fat, especially in the abdomen.

SLEEP & BRAIN FUNCTION

Just one night of sleep deprivation Is enough to impair activity in your frontal lobe, which controls complex decision-making. 

Skimping on sleep sets your brain up to make bad decisions. It dulls activity in the brain’s frontal lobe, the locus of decision-making and impulse control.

So it’s a little like being drunk. 

You don’t have the mental clarity to make good decisions.

CHANGE IN YOUR FAT CELLS

Your brain and body that feel exhausted, dazed, confused—your fat cells do too. When your body is sleep deprived, it suffers from “metabolic grogginess.” The term means that the hormones that control your fat cells don’t feel the same way.

LACK OF SLEEP - ENEMY OF MUSCLE

Unfortunately, the disastrous impact spreads beyond diet and into your workouts. No matter what your fitness goals are, having some muscle on your body is important. Muscle is the enemy of fat—it helps you burn fat and stay young. But lack of sleep is the enemy of muscle. Sleep debt decreases body’s ability to make muscle, causes muscle loss, and can lead to a higher incidence of injuries.

WHAT HAPPENS TO YOU?

  • When people were starved of sleep, late-night snacking increased, and they were more likely to choose high-carb snacks.
  • Sleeping too little prompts people to eat bigger portions of all foods, increasing weight gain. Poor sleep has repeatedly been linked to a higher body mass index (BMI).
  • Harder to make healthy choices and resist tempting foods.
  • People who get poor sleep tend to consume more calories.
  • Poor sleep can also increase your calorie intake by affecting your ability to control your portion sizes. Sleep deprivation may lower your RMR. 
  • Your resting metabolic rate (RMR) is the number of calories your body burns when you're completely at rest. It's affected by age, weight, height, sex and muscle mass.
  • You're more likely to get tired earlier during physical activity. Poor sleep can cause cells to become insulin resistant.