Metabolic Health 5 MIN READ

Can Intermittent Fasting Improve Metabolic Health?

Intermittent fasting (IF) is a pattern of time-restricted eating. When practising IF, one confines food intake during certain hours and consumes food in designated eating windows.

Written by Team Ultrahuman

Sep 10, 2021
intermittent fasting metabolic

Intermittent fasting (IF) is a pattern of time-restricted eating. When practising IF, one confines food intake during certain hours and consumes food in designated eating windows. It does not require a person to give up any particular food group. According to Harvard Health, studies in humans have shown that IF is safe and effective.

Considering the fact that many individuals find abstaining from food difficult, the period of fasting is key. It makes IF a more realistic, sustainable, and promising approach for dealing with obesity, as well as for better metabolic health.

intermittent fasting health

Types of Intermittent Fasting

There are many ways to practice intermittent fasting like splitting 24 hours or 7 days of the week into eating and fasting schedules. Here are some of the most popular methods:

  • The 16/8 method: Also called the Leangains protocol, 16:8 fasting entails fasting for 16 hours a day and eating during the remaining 8 hours. It usually involves skipping breakfast and limiting the calorie consumption period to 8 hours.
  • Eat-Stop-Eat: This is another type of fasting that lasts for 24 hours, once or twice a week. People usually eat until dinner and fast until dinner, the next day.
  • The 5:2 diet: This interesting method follows calorie restriction allowing you to consume 500–600 calories on two nonconsecutive days of the week but on the other five days, the arrangement allows you to eat without a calorie stipulation.

As with most diets that reduce your calories, IF methods may help reduce your weight. It’s important however to not go overboard on the rest of the eating days. Overcompensating by eating a tub of ice cream on off days while following a strict fasting protocol on the IF days will still derail your weight loss journey. We have all been there. Instead, a reward at the end of the week with a small measured portion of your favourite food will help you stay on track as well as allow you to enjoy the fruits of your labour.

Metabolic Health

Hormones are chemical substances secreted directly into the blood by the endocrine glands in meagre amounts. They act as molecular postmen. They are responsible for many bodily functions like development and growth, cognitive and sexual function, and metabolism. They also play a critical role in managing your weight! Hormones like ghrelin and leptin have a strong influence on your appetite, the number of calories you consume and how much fat you can store or burn, according to a study by M.D. Klok et al Hence it is crucial to look at your health from the lens of metabolic fitness. 

According to various studies, intermittent fasting has been connected with improvements in the balance of some of the fat-burning hormones. IF could be an important tool for some individuals to manage weight. Some studies have also shown that when you lose weight, your metabolic rate declines because losing weight causes muscle loss, and muscle tissue burns calories around the clock. But the reduction in the metabolic rate seen with weight loss can’t always be explained by muscle mass loss alone.

intermittent metabolic health

Let’s look at some of the hormones, their functions and how intermittent fasting affects them:


Insulin is one of the critical hormones involved in fat metabolism. It is also the hormone that maintains your metabolic fitness. It informs your body to conserve fat and also prohibits your body from breaking it down. Having high levels of insulin can make the quest for weight loss difficult.

Higher levels of the insulin hormone have been linked with various diseases such as type 2 diabetes, obesity, cancer and heart disease. Studies show that lowering your insulin levels through intermittent fasting can be as effective as many other calorie restriction diets.

In fact, alternate-day fasting lowered levels of fasting insulin and insulin resistance to a greater degree than calorie restriction among overweight and obese adults with insulin resistance, according to findings published in Obesity.

Human Growth Hormone

Human growth hormone (HGH) produced by the pituitary gland stimulates growth, cell regeneration, and cell reproduction.

HGH is an important hormone for the maintenance, maturation and repair of healthy tissue in the brain and other organs. It can also help in building muscle mass, advancing metabolism and burning fat.

Studies have shown that fasting can potentially cause a rise in levels of the human growth hormone. Since it is an important hormone for fat loss, the evidence of the surge is encouraging for individuals considering fasting.

A study by Hartman et al showed that levels of the human growth hormone increased five-fold in men, in response to a 2 day fast. Increases in the human growth hormone in blood levels are shown to not only promote fat burning but also preserve muscle mass, among many other benefits.

A number of studies indicate that women don’t always experience similar benefits from fasting as men do. They need to subscribe to a modified approach. It is also unclear from current studies whether women enjoy the same ascent in the human growth hormone.

intermittent fasting improve


Norepinephrine, produced by the adrenal gland, serves as a stress hormone as well as a neurotransmitter, a chemical sending signals between nerve cells. It’s released into the bloodstream when the brain perceives the onset of a stressful event.

Norepinephrine plays a part in the body’s response to stress by:

  • increasing heart rate
  • triggering the release of glucose (sugar) into the blood
  • increasing blood flow to the muscles

Norepinephrine is involved in the “fight or flight” response, our evolutionary survival mechanism that helps us confront a threatening situation or move away from it. Norepinephrine is one of the primary activators of fasting-induced lipolysis, a process that mobilizes stored energy during fasting or exercise and reduces the volume of fatty tissue.

According to a study, resting energy expenditure increases in early starvation, accompanied by an increase in plasma norepinephrine. This upswing in norepinephrine seems to be due to a decline in serum glucose and maybe the initial signal for metabolic changes in early starvation.


One of the main benefits of fasting is the decline in insulin and the corresponding upturn in nor-adrenalin, cortisol, and the growth hormone. Studies examining the effects of intermittent fasting on metabolism are still inconclusive. Early studies have shown that short-term fasts can boost metabolism by as much as 14%, and several studies suggest that muscle mass doesn’t decrease much with intermittent fasting when paired with balanced nutrition. If more studies validate these findings, then intermittent fasting could have several important weight loss advantages over calorie restriction diets.

*However, it’s always important to consult with your doctor if you plan to make any dietary changes.*



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