Science behind intermittent fasting
Afifa Khan - Nutrition Coach
As an accredited Nutrition and Health Coach, Afifa has been coaching and counseling clients for many years with scientific and holistic approaches. She is extremely passionate about lifestyle modification from a very young age. Afifa has transformed her life and many others with her expertise in nutritional interventions, diet consultation, weight management, and Sports Nutrition
04.10.22

Science Behind Intermittent Fasting: Is Intermittent Fasting a Good Way To Lose Weight?

Intermittent fasting (IF) has spread across social media and in the fitness world sphere as one of the most effective diet trends for weight loss Though fasting has been practiced for religious and activism purposes throughout history, intermittent fasting for weight loss and health is relatively new thanks to current intermittent fasting research. IF is an eating habit where food intake is restricted to a certain window of time each day. IF diet reviews claim it significantly aids in weight loss as well as lower insulin, cholesterol, and inflammation levels. But what does science say about IF? How does it work and is intermittent fasting good for weight loss?

Table Of Contents

How Does Intermittent Fasting Work?

IF works by restricting your daily eating to a certain window of time. The goal is to fast for a longer period than you eat. IF is different from traditional fasting where one would go without food for a 24-hour period of time or more (however some IF methods do involve 24-hour fasts). What hours you choose to eat versus fast are up to you but generally, people choose to eat during the earlier part of the day and fast at night. For example, one IF method is the 16:8 approach where you restrict eating to 8-hours a day, say 12pm to 8pm, then fast until the next day 16 hours later. 

Science behind intermittent fasting

There are no specific intermittent fasting rules beyond sticking to your fasting and eating window. During your eating period, you can eat what you like. For this reason, IF sounds like an attractive dieting method to most people. There are no rules that restrict what you can eat just when you can eat. However, it’s suggested that you eat sensibly during your eating window and not overcompensate by binging on unhealthy food. Intermittent fasting is considered safe for all adults 18 and over unless they are pregnant, breastfeeding, are taking medicine, or have other health concerns. 

Types of Intermittent Fasting

There are several ways you can follow an IF eating schedule:

16:8: The 16:8 IF schedule involves eating during an 8-hour period followed by 16 hours of fasting. Alternatively, you can instead follow an 18:6 schedule and restrict your eating to only 6 hours followed by an 18 hour fast. Some people may choose to eat during only a 4-hour window followed by a 20 hour fast. How you schedule your eating and fasting windows are up to you. 

Alternate day fast: An alternate day fasting schedule has you eating normally followed by a day of fasting or restricted eating. So, for example, you would eat normally today then tomorrow fast or restrict your calories to only 25% of your normal caloric needs. You would then repeat this schedule every other day throughout the week. To determine your daily caloric needs, use a calorie and BMI calculator

500:2: The 500:2 method involves eating only 500 calories 2 days out of the week while eating normally on the other days. For example, eating normally Monday, Tuesday, Thursday, Friday, and Sunday then eating only 500 calories on Wednesday and Sunday. 

24-hour fast: The 24-hour fasting method involves doing a full 24-hour fast once or multiple times a week. The other days of the week you eat normally. 

The Science Behind Intermittent Fasting

What is the science behind intermittent fasting? Here’s what scientists have to say about why intermittent fasting works for weight loss and how it benefits your health. Both animal and human studies have shown that IF can result in weight loss and reduce symptoms of other health conditions such as diabetes, asthma, and inflammation. One study in particular took overweight adults with asthma who were subjected to eating 20% of their normal daily caloric intake on alternate days, for eight weeks. After the trial, participants lost on average 8% of their body weight and reduced their symptoms of asthma, inflammation, and oxidative stress. 

How Does IF Impact Weight Loss?

There are a couple ways IF may lead to weight loss in humans. For one, IF can help decrease insulin levels in the blood. Insulin is a chemical that helps your body store sugar in your cells. The higher your insulin levels, the more sugar your cells will absorb and store as fat. Eating continuously throughout the day, particularly refined grains, and sugars, will keep insulin levels higher. When your body is in a fasted state for a prolonged period (10-16 hours), insulin and blood sugar levels drop. When insulin levels are low, your fat cells can then release sugar into your bloodstream to be burned off for energy. Thus, resulting in fat loss. 

By intentionally prolonging time between meals or eating periods, you exhaust your body’s sugar stores which forces it to burn fat for fuel instead. Unfortunately, many of us in modern society never stop eating long enough for our insulin and sugar levels to drop. Continuous snacking and late-night eating ensure your body has a constant supply of fuel to burn. Another way in which IF can help you lose weight is by reducing the time you spend eating which in turn, reduces your overall calorie consumption. 

Benefits of Intermittent Fasting

An intermittent fasting by age chart may show the benefits of IF at different ages, particularly in men and women over 40 who are more prone to dietary and lifestyle health concerns (such as diabetes and obesity). However, the benefits of IF are shared by people of all ages. One such benefit may be in reducing risk of diabetes. There is a positive correlation between intermittent fasting and diabetes. One study involving obese pre-diabetic men, showed that IF during an 8-hour period (7am to 3pm) dramatically decreased insulin levels and insulin sensitivity after just 5 weeks. The control group of obese pre-diabetic men were fed during a period of 12 hours with no significant changes in insulin levels or sensitivity. 

There’s also evidence based on studies that show IF may help reduce risk of heart disease, cancer, obesity, tissue damage, and improve cognitive function. One of the few concerns with IF is its effect on metabolism. Does intermittent fasting slow metabolism? According to research, IF doesn’t negatively impact metabolism any more than conventional calorie restricted diets that cause weight loss. 

Is Intermittent Fasting Good for Weight Loss?

Intermittent fasting can be helpful for weight loss however, it is not a magic pill. In a study with rats, researchers subjected the animals to two 24-hour fasting periods per week. On days the rats were allowed to eat, they overate to compensate. The result showed no improvement in weight loss or health. Intermittent fasting may help you lose weight due to a caloric deficit but if you overeat on caloric foods and beverages during your feeding window, you’re unlikely to see results. Intermittent fasting is not meant to be an excuse to eat unhealthily. IF works best when combined with healthy lifestyle habits, like a balanced diet. If you’re unsure what a balanced diet looks like for you, consider speaking to a nutritionist.

IF is meant to be treated as a lifestyle or eating pattern rather than a diet. Some people may find that IF helps them to eat in a more structured manner, thus helping them nix bad eating habits like snacking and late-night eating. Intermittent fasting may also be more effective when combined with the ketogenic or, keto, lifestyle. Keto with intermittent fasting combined can help your body produce more chemicals called ketones, which provide fuel for your body in place of carbohydrates. Both keto and intermittent fasting help lower insulin levels and burn more fat instead of carbohydrates. Combining the two methods of eating may lead to more fat loss than IF on its own but more research is needed to know for sure. 

Should You Try Intermittent Fasting?

Intermittent fasting is a method of eating that may improve your health and aid in weight loss. It’s generally safe for most adults who are not pregnant, breastfeeding, or have other medical concerns. Some people find that IF helps them to restructure their eating habits and eat fewer calories which results in weight loss. However, conventional calorie restricted diets may be just as effective. 

Whether you should try IF for weight loss depends on your personal preferences. For some, restricting their eating to a small window of time is too difficult in which case, a conventional diet plan may work better. Other people may find IF easier to stick to because they have less factors to consider (such as meal planning, calorie counting, or macro tracking) and focus on when they eat rather than what. The bottom line remains that a healthy balanced diet is key for significant fat loss and health improvement. Should you try intermittent fasting for weight loss, make sure you are following proper nutrition guidelines. 

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As an accredited Nutrition and Health Coach, Afifa has been coaching and counseling clients for many years with scientific and holistic approaches. She is extremely passionate about lifestyle modification from a very young age. Afifa has transformed her life and many others with her expertise in nutritional interventions, diet consultation, weight management, and Sports Nutrition