IS FASTING THE SECRET TO WEIGHT LOSS?

It seems that as a population we have more weight and less time than ever.

As the battle against our sloppy rigs and lack of effort to count every damn calorie we consume continues, a new weight loss trend has emerged. Intermittent fasting.

But can intermittent fasting really accelerate weight loss? Here’s what the research says.

What is Intermittent Fasting?

Intermittent fasting isn’t a traditional diet in the sense that your excluding certain food groups, but rather excluding certain times of the day in which you can eat.

Due to these restricted eating times participants generally consume 10-30% less calories than usual, even when not regulating their food consumption on non-fasting days. [2]

The most common methods of intermittent fasting are:

Alternate Day Fasting

Fasting every other day (fasting days can include one small meal up to 500 calories and non-fasting days consist of a regular, healthy diet).

5:2 Fasting

Regular eating for 5 days and fasting for 2 days (same rules apply as above).

Time-Restricted Eating

Daily fasting and eating within a set time frame (the eating window typically lasts for 8 hours  such as 11am to 7pm).

These methods are thought to enable the body to switch from burning glucose to burning fat, inducing a process called metabolic switching – the potential key to weight loss.

How Effective is Intermittent Fasting for Weight Loss?

Recent studies have shown that alternate day and 5:2 fasting can result in weight loss of 4-8% and time restricted eating 3-4% over an 8–12-week period. [3]

This suggests that alternate day and 5:2 fasting methods are the most effective, likely for one simple reason – the fasting periods last for more than 12 hours.

If we think back to our slightly uglier and more primitive hunter-gatherer ancestors, they would have often experienced extended periods of time without food or water. As they adapted to the unpredictability of their next meal for the purpose of survival, we no longer bear this issue, which has now created a new one. So are we destined to be fat?

One particular recent review focused on the effects of intermittent fasting on overweight and obese participants. All 27 studies demonstrated weight loss from 0.8-13% even with ad lib eating days, an average BMI reduction of 4.3%, and a decrease in waist circumference by 3-8cm in studies longer than 4 weeks. [5]

It is also important to note that studies which combined fasting with calorie restriction or monitoring on non-fasting days showed greater weight loss than fasting alone. [5]

Are There any Other Benefits of Intermittent Fasting?

Intermittent fasting is associated with reductions in systolic (blood pressure whilst the heart is beating) and diastolic (blood pressure whilst the heart is resting) blood pressure, particularly in individuals with elevated baselines (hypertension). [2]

Improvements in glycaemic control (blood sugar regulation), fasting glucose levels (blood glucose levels after fasting for 8-10 hours), and insulin sensitivity (counteraction to glucose), have been reported which may help manage or prevent type 2 diabetes. [2]

It assists with visceral fat (the dangerous type) and truncal fat (belly fat) loss which improves adipokine regulation (monitors metabolism, inflammation and appetite). [4]

Reductions in oxidative stress (bodily stress causing cellular and tissue damage) and inflammation, which are common in obese individuals, are sighted. The release of adiponectin (a hormone which helps regulate glucose and break down fatty acids) which has anti-inflammatory properties, is increased during fasting periods. [4]

Results vary regarding the effect on LDL (bad) and HDL (good) cholesterol. [3]

How Does Intermittent Fasting Work?

One particular study explored precisely how fasting influences metabolism through metabolic switching – the shift from using glucose as an energy source to fatty acids and ketones, which usually occurs after 12 hours of fasting, initiating fax oxidisation. [4]

What all this means is instead of using carbohydrates the body is burning fat for energy.

Not only does metabolic switching promote fat loss, but it also promotes autophagy (the clearing out of damaged cells), which may improve cellular health and longevity. [2]

It is important to note that the key to long-term success depends on a number of factors, and most importantly that you can maintain a negative energy balance. [1]

Is Intermittent Fasting Sustainable?

One of the biggest challenges with traditional calorie-restricted diets is adherence – many people find it difficult to stick to these diets long-term. Intermittent fasting, on the other hand, offers a more flexible and sustainable approach.

With its lack of calorie tracking, intermittent fasting methods are more convenient, and less tedious than diets based on macronutrient composition or food group restriction.

Studies suggest that adherence to intermittent fasting is relatively high. In a trial that followed participants over 12 months, over 70% were able to stick to their protocols. [4]

Sounds Great, But Are There Any Side Effects?

First and foremost, intermittent fasting is safe.

However, throughout the studies conducted some participants recorded mild symptoms such as headaches, dizziness and fatigue during the adjustment phase (first 1-2 weeks). [3]

It is not recommended that certain populations such as pregnant women, individuals with eating disorders, and those with chronic health conditions attempt to take part. [4]

Concerns about binge eating and purging during non-fasting days were not observed – some participants even reported improved body image and mood during the trials. [5]

It is important to maintain a healthy, diverse, nutrient-dense diet during fasting periods to ensure that individuals meet their nutritional needs. [2]

No Worries, But Will Fasting Affect My Gains?

Exercising whilst fasting is safe, though some participants reported reduced energy and therefore intense exercise should be dedicated to regular eating days if possible. [2]

Weight loss from intermittent fasting follows the typical pattern seen in caloric diets being a reduction of 75% fat mass and 25% lean mass. Fasting therefore isn’t detrimental to building muscle, however it probably isn’t optimal either for sheer muscle-gain. [3]

So, is Intermittent Fasting the Secret to Weight Loss?

Overall, intermittent fasting is an effective weight loss strategy.

Now admittedly, there is no such secret. Intermittent fasting works because of its practicality when restricting calories and in this realm, consistency is everything.

So long as you are consistently using more energy than you consume, you will lose weight. How you go about it is completely up to you and intermittent fasting is simply another tool at your disposal – quite a good one in my opinion.

There is certainly a need for longer studies (more than 1 year) in assessing the long-term efficacy of such diets, but if you need to drop some weight, why not give it a go.

If you’re interested in trying intermittent fasting, start slow. Try time-restricted eating by eating within a 10–12-hour window, then gradually reduce it as your body adapts. Always consult with a healthcare professional before making significant dietary changes.

Ultimately, intermittent fasting might just be the key to a healthier you – without the hassle of constant calorie counting.

References

[1] Freire, R. (2020). Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting, and popular diets. Nutrition, 69, 110549.

[2] Varady, K. A., Cienfuegos, S., Ezpeleta, M., & Gabel, K. (2021). Cardiometabolic benefits of intermittent fasting. Annual review of nutrition, 41(1), 333-361.

[3] Varady, K. A., Cienfuegos, S., Ezpeleta, M., & Gabel, K. (2022). Clinical application of intermittent fasting for weight loss: progress and future directions. Nature Reviews Endocrinology, 18(5), 309-321.

[4] Vasim, I., Majeed, C. N., & DeBoer, M. D. (2022). Intermittent fasting and metabolic health. Nutrients, 14(3), 631.

[5] Welton, S., Minty, R., O’Driscoll, T., Willms, H., Poirier, D., Madden, S., & Kelly, L. (2020). Intermittent fasting and weight loss: Systematic review. Canadian Family Physician, 66(2), 117-125.