Healthy Fasting For Weight Loss


Maintaining a healthy weight is an important part of staying healthy and preventing heart disease, high blood pressure, type 2 diabetes, and other diseases. Maintaining a healthy weight involves eating right, exercising regularly, and choosing a diet that best suits your body type.

What is fasting?

Fasting involves the abstinence from all or some food and drink for a given period of time. Despite being popularised by today’s diet world, the practice of fasting dates back centuries and is thought to be one of the oldest therapies in medicine. It plays a central role in cultural and religious practices, with all major religions partaking in one form or another.

Whether it involves the abstinence of food and drink or a lighter, lower-calorie form of eating, many argue that going without food for periods of time is something we have evolved to do.


Intermittent fasting can be effective in reducing body weight in people of every size, according to a report in Nutrition Reviews(opens in new tab). Most studies focused on alternate day fasting or whole-day fasting trials, but there is also evidence to support the success of time-restricted eating. As well as weight loss, intermittent fasting can have cardiometabolic benefits for those with obesity, as found in another review in the 2021 Annual Review of Nutrition

Similar to the way the keto diet helps with weight loss, intermittent fasting can put you into a state called ketosis where you are using ketones as fuel. A study in the journal of Cell Metabolism indicates that in the state of ketosis, the body metabolizes fat and produces ketones, which the body can use as an alternative energy source.

“After a meal, you pass through four different metabolic states as your body digests the food,” explains Dr Deborah Lee, MD, from Dr Fox Online Pharmacy(opens in new tab). “These are: the fed state, the post-absorptive state/early fasting state, the late fasting state, and starvation.

Dr Deborah Lee, MDMedical Doctor

Having worked for many years in the U.K’s National Health Service, initially as a GP, and then as Lead Clinician for an integrated Community Sexual Health Service, Dr Deborah Lee now works as a health and medical writer, with an emphasis on women’s health. She is a menopause specialist. 

“Most of the time your body uses glucose for energy. After a meal, glucose levels rise, and fat is stored as triglycerides in adipose tissue. In the normal situation, the body uses glycogen stored in the liver for energy. However, after 12 hours of fasting, all the liver glycogen has been used up. The body is now forced to take triglycerides from adipose tissue and break these down into fatty acids and glycerol. Fatty acids are converted into ketone bodies, which are then used for fuel, as an alternative to glucose.”

She adds that when the body passes from the post-absorptive to the fasting state, this is referred to as ‘the metabolic switch.’ 

“It is at this point, when the switch is turned on, that the body starts to use ketones for energy,” she says. “In the fed and post-absorptive state, the primary hormone is insulin, whereas in the fasting state, the primary hormone is now glucagon.”

Intermittent fasting also works by restricting your overall calorie intake and putting you into a calorie deficit (where you are using more calories than you are consuming) . Even if you eat more after your fast, you are unlikely to eat as much as you would in a normal eating pattern. A calorie deficit is one of the most effective ways to lose weight, according to a report in the Journal of Obesity and Metabolic Syndrome so this aspect of intermittent fasting may also help you to lose weight.


Dr Sam Watts, founder of Mind Body Medical(opens in new tab), tells Live Science that there are two clear leaders when it comes to intermittent fasting styles. “Lots of clinical evidence exists around the potential weight loss benefits of different intermittent fasting plans,” he says. “For quicker and more profound weight loss, the alternate day fasting plan is arguably the most effective. A less-extreme and thus easier-to-adopt approach is the 16:8 model. This is a time-restricted eating version of intermittent fasting that involves consuming all of your calories in an eight-hour window and fasting for the remaining 16 hours. 

“This approach has consistently been shown to induce significant and progressive weight loss in an arguably more sustainable model.”


Twenty-four-hour fasting is one of the toughest fasting styles, where you fast completely, or heavily restrict calorie intake for 24 hours, often for one or two days a week. This may not be the best method of fasting for a lot of us, as it isn’t compatible with many lifestyles, and longer periods of fasting (48-72 hours) can trigger a starvation response, which can encourage your body to store fat when you do eat. 


This style of fasting is a flexible fasting style where you fast two days a week and eat normally the rest of the time. On fasting days you restrict your calorie intake to 500-600 calories, generally consuming this in one meal at the start of the day and then fasting until the next morning.


With alternate day fasting, you fast every other day, eating to satiety on alternate days. On fasting days you will typically consume up to 800 calories a day, although some people choose to fast completely. 

“Using this approach, you fast every other day while eating a healthy, well-balanced diet on the alternate non-fasting days,” says Watts. “This approach has been shown to facilitate significant and progressive weight loss.”

TIME-RESTRICTED EATING: 20:4, 16:8, 14:10, 12:12

Time-restricted eating is a fasting style where you fast for a certain amount of time and eat in the remaining window. Common types of time-restricted fasting include 20:4, 16:8, 14:10 or 12:12, with the first number being the fasting window and the second number the eating window. There isn’t evidence to suggest any particular benefit to one over the other, and it is worth experimenting to find what works best for you.

Disadvantages of Fasting for Weight Loss

Fasting has been around for a while. Mostly used for religious purposes it is also considered a technique to lose weight. Some people also use it as a detox mechanism but the fact is there are organs & natural foods that are already doing that job.

Do you think then fasting is the right & effective approach to weight loss?Let us explain through facts whether fasting is good for you or not.

There are different definitions of fasting. Some people fast without any foods or water at a stretch while some are flexible and allow themselves to have raw fruits, water & caffeine. Fasts lasting a day or two are unlikely to be dangerous for most healthy adults. But the following people like the elderly, anyone with a chronic disease, pregnant women, and children fall under the high risk category and are advised against any type of fasting.

Fasting can be dangerous if followed for prolonged periods, anywhere from three days to a month. What happens to your body when you fast?

You lose weight. But that’s because you have drastically cut down on your calories. Also you are not losing fat this instance instead that change on the weighing scale is reflecting the loss of water in your body. Remember our body is 70 % water and that’s why on a fast one loses the “water weight” which comes instantly back the minute eating is resumed. Fasting also slows down the metabolism that’s the reason why a lot of people tend to put on weight even when they have been on prolonged periods of fasting instead of really losing it.

Next time you are thinking about fasting to lose weight you might want to reconsider going through that route especially when the end results can this discouraging.

The healthy and the most effective way to lose weight are to get into a routine of healthy diet and regular exercise. Following a balanced routine not only leads to a healthy weight loss but also a fit and toned body.

The Science of Fasting

A large body of evidence now supports the benefits of fasting, though the most notable data has been recorded in studies with animals. Even so, these findings are promising for humans. Essentially, fasting cleanses our body of toxins and forces cells into processes that are not usually stimulated when a steady stream of fuel from food is always present.

When we fast, the body does not have its usual access to glucose, forcing the cells to resort to other means and materials to produce energy. As a result, the body begins gluconeogenesis, a natural process of producing its own sugar. The liver helps by converting non-carbohydrate materials like lactate, amino acids, and fats into glucose energy. Because our bodies conserve energy during fasting, our basal metabolic rate (the amount of energy our bodies burn while resting) becomes more efficient, thereby lowering our heart rate and blood pressure.

Ketosis, another process that occurs later into the fast cycle, happens when the body burns stored fat as its primary power source. This is the ideal mode for weight loss and balancing blood sugar levels.

Fasting puts the body under mild stress, which makes our cells adapt by enhancing their ability to cope. In other words, they become strong. This process is similar to what happens when we stress our muscles and cardiovascular system during exercise. As with exercise, our body can only grow stronger during these processes when there is adequate time to rest and recover. That’s why short-term fasting is recommended.

Top 5 health benefits of fasting

1. Supports blood sugar management

Several studies support the use of fasting as a means of improving blood sugar control and potentially reducing the risk of diabetes, although gender may play a part and more studies are needed.

2. May help disease prevention

Lightening your normal eating pattern appears to give your body the time to focus on other important functions, including disease prevention. With this in mind, it may also improve the body’s ability to manage chronic inflammation and, as such, reduce the risk of conditions such as heart disease, multiple sclerosis and rheumatoid arthritis.

3. May support brain function

Studies in animals suggest fasting may protect against and improve outcomes in Parkinson’s and Alzheimer’s, as well as improve brain function by supporting memory and brain processing. Similarly, animal studies suggest fasting may protect brain health and increase the production of nerve cells.

Human studies report fasting may reduce symptoms of anxiety and depression and improve social connection.

More studies are needed to assess these effects but findings to date are encouraging.

4. May delay ageing and support growth and metabolism

Fasting, and in particular adopting a diet low in protein, has in animal studies been associated with an extended life expectancy.

Furthermore, fasting appears to promote levels of human growth hormone, a hormone that plays an important role in growth and repair, metabolism, weight loss, muscle strength and exercise performance.

Current longevity research is largely limited to animals, so more studies are needed to fully understand how this may impact human ageing.

5. May support weight loss

Many dieters turn to fasting as a manageable approach to weight loss. Studies show that controlling the times we eat or undertaking short-term fasts can aid weight reduction, fat loss and improve blood lipids. That’s not all: other studies have shown fasting to increase the ability to switch metabolism to fat burning, preserve muscle mass and improve body composition in overweight people.

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