Intermittent Fasting to Boost the Metabolism (Fact or Fiction?)

Different diets have always enjoyed the spotlight in both the mainstream media and health and fitness circles.

While many of these have fitted the criteria of the ‘fad diet,’ there have been a few types of dieting that have proven beneficial for those looking to improve their health, boost their physique, or increase their fitness. (1)

Intermittent Fasting

One of the newer diet methods to enter this spotlight is intermittent fasting. Intermittent fasting consists of a 16-hour fasting window and an 8-hour feeding window within a 24-hour time period. Sleep is included int he 16-hout fasting window. Despite the relatively little research on this version, early studies suggest that the 16-8 form is indeed as beneficial, if not more beneficial, for weight and fat loss as conventional calorie cutting. (2)

This type of diet is one of the more unique forms of structured eating. This is because it is one of the only diets that doesn’t restrict or forbid certain nutrients or foods, nor does it instruct you to decrease your overall food intake.

The benefits afforded through this diet are thought to be due to both an increase in metabolism during the fasting period, and the timing of meals more towards the evening, which could help promote fat loss due to a balance of hormones caused by the circadian rhythm. (3)

There is also more research on some different types of intermittent Fasting than others, despite studies on this form of dieting still being one of the more underrepresented in the field of health and fitness science.

So, to give you a full picture of intermittent fasting, how it works, and whether you should consider using it, we put together a guide below to see if intermittent fasting can help you lose weight and boost your metabolism to improve your health and body composition.

Benefits of Fasting

Intermittent fasting, or the act of eating on alternate or consecutive days with corresponding feeding/fasting windows, has been reported to facilitate the following health benefits:

  • prevent the progression of type 2 diabetes
  • reduce risk of cardiovascular disease
  • increase longevity
  • reduce risk of developing circadian rhythm disorders
  • reduce risk of developing neurological disorders
  • reduce inflammation
  • attenuate immune cells
  • improve lipid levels and circulating glucose
  • reduce blood pressure
  • reduce oxidative stress
  • improve the efficiency of the metabolism

Other Methods of Intermittent Fasting

As mentioned above, there are many different types of intermittent fasting that are used and have been studied. These are all reviewed below:

1. Alternate Day Fasting (ADF)

This form of intermittent fasting is structured exactly as the name implies, involving fasting for one day, following by a ‘free day’ of eating to satisfaction, before repeating the day of fasting again. It should be noted that during the fasting days, a restricted calorie intake of 500 calories is prescribed as a general guideline. More than this is considered breaking the fast.

This is one of the most researched versions of fasting. It has also been shown to be a very effective form of the diet, with weight loss of up to 2.5%, and fat loss of up to 4% in only 3 weeks. (4)

It is thought that these effects are due to the massive gap in calories that is caused by the day of fasting that doesn’t seem to be offset by the higher-calorie feeding days. This causes a breakdown in fat and may offer a host of health benefits, including increased insulin sensitivity and lower blood sugar.

However, while it is highly effective, it is also one of the tougher versions to do, with hunger being a significant issue throughout the diet. So, this may be a better option for the more seasoned dieters only.

2. 20-4 Warrior Diet

The Warrior Diet is very similar to the Lean Gains protocol mentioned above. Dieters have a 4-hour feeding window, and then the rest of the 24-hour day is spent fasting. This has almost no research done on it directly, with most relying on studies done during Ramadan, where a similar timeframe of eating and fasting takes place.

Nonetheless, whether looking at this form of intermittent fasting as a longer version of the Leangains method, or as a similar practice to Ramadan, it has been shown to be effective for weight and fat loss. (5) However, it is neither as effective as Alternate Day Fasting, nor as easy to do as the Leangains form. It can also have some detrimental effects on mood. (6)

3. 5:2 Fasting

This is the most unbalanced form o fasting, with regular eating taking place five days per week, and fasting taking place on any two days out of the week. These days can be separated in any way, or joined together.

Like the Warrior Diet, there’s little research looking at this particular form of intermittent fasting. However, testimonials seem to suggest it has an effect that lies between the Lean Gains and Alternate Day Fasting methods. (7,8)

Take Home Points

Fasting can be used effectively to help you lose fat and get healthier. This could be due to a number of mechanisms in the body, including increased insulin sensitivity, stable energy levels, better adherence to the diet, better nutrient partitioning, increased metabolic rate, and increased fat oxidation.

Some versions have been better researched than others, and seem to work better than others when executed properly. However, all forms work to some extent. That said, don’t be afraid to experiment and see what works best for you. Start with easier protocols and gradually increase your fasting periods to avoid the negative effects associated with prolonged periods of fasting.

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