Intermittent fasting has become popular due to the convenience it offers. It sounds great on paper. One doesn’t have to bother eating 6-7 meals a day. People are achieving results without sitting and counting calories from each meal. Not to mention the economic benefits of saving both time and money in shopping,cooking and eating. Besides there is the added advantage of not having to worry about “low carb high fat”, vs “high carb low fat”, eating options are more flexible. While the trend of intermittent fasting has caught on worldwide, skeptics are worried about muscle wastage. Is it a legitimate concern? Or does intermittent fasting actually help you lose fat rather than muscle?
Intermittent Fasting : The Basics
Intermittent fasting contrary to popular notion is not a diet. Neither is it equivalent to caloric restriction as many health experts claim. The process of intermittent fasting involves not eating for a period of 16-72 hours. Ideally one should consume only water during the fasting phase but a small cup of black coffee without sugar, tea without cream and sugar (green or black is your choice) are allowed. The 5:2 diet cannot be classified under intermittent fasting because it simply restricts calories two days a week. Eating during fasting, even if it is low calorie will deprive you off the benefits of fasting.
According to the American Heart Association, intermittent fasting helped overweight individuals to lose weight, lower triglyceride levels, lower LDL levels (among those who had high LDL) and reduce insulin resistance. A recent study(2019) published in the New England Journal of Medicine found that intermittent fasting interventions in human can help reduce obesity, insulin resistance , hypertension and inflammation. It is clear that intermittent fasting has a lot of health benefits. However, two common myths on intermittent fasting often intimidates someone curious to try it out. The first concern is regarding blood glucose. Does intermittent fasting cause a shortage of blood glucose ? Secondly, many people seem to believe intermittent fasting will lead to muscle wastage.
Muscle Wastage: What does the science say
In order to understand why we fear muscle wastage during fasting it is essential to understand a few biochemical processes. Our brain uses glucose as the prefered source of fuel. Certain other parts of the human body like the red blood cells exclusively run on glucose.. Hence one may fear if we do not have a constant supply of glucose we will be in trouble. However, as I mentioned in a previous article, our body manufactures glucose even without a single morsel of food entering the body . During gluconeogenesis amino acids and free fatty acids are broken down to produce glucose. Naturally one would think if we are not eating we would start wasting muscle as gluconeogenesis would be accelerated. However, this is not what happens in reality.
In 2009, researchers looked at the effects of intermittent fasting in a group of obese individuals. 16 obese individuals (12 women , 4 men) who underwent a 10 week trial period of alternate day fasting. As the name suggests participants ate on alternate days. The subjects did not make any additional efforts to preserve or build muscle such as strength training. They did not follow a high protein diet. At the end of the trial period, scientists observed at all the weight loss was due to fat loss. Muscle mass was preserved. The researchers were intrigued by the results. A follow up trial was published in the International Journal of Obesity in which women were studied for effects of intermittent fasting on weight loss vs caloric restriction. The women in the calorie restricted group lost 5.6 kg while the women in the intermittent fasting group lost 6.4 kg. The fat loss in both groups was 79% of the total weight. Thus intermittent fasting is comparable with calorie restriction in rates of muscle loss.
A meta analysis which was carried out on twenty eight studies actually found that alternate day fasting was actually superior to calorie restriction in preserving muscle mass. A meta analysis essentially is a study of different studies which results in elimination of a lot of biases. In terms of evidence meta analysis and systematic reviews are considered the gold standard, followed by randomized control trials, observational studies with the least credible being personal experiences, anecdotes and opinions . The study concluded that fasting was just as effective as calorie restriction in improving biomarkers and maybe superior due to the relative ease of compliance , greater fat-mass loss and relative preservation of fat-free mass. In light of these results one can conclude with relative certainty that fasting will not result in muscle wastage.
The major drawback of these studies is the fact that they were carried out on obese individuals. Obese individuals have large amounts of fat reserves. One may ask what about normal weight individuals or athletes? Are they are a risk of muscle wastage during fasting.
Athletic individuals need not fear fasting
In 2016, researchers compared the effects of intermittent fasting with normal diet for eight weeks in men who underwent resistance training. The total amount of calorie consumption was kept constant. Both groups were also matched for macronutrient intake . The intermittent fasting group consumed their meals at 1 pm , 4 pm and 8 pm and fasted the rest of the day. The calorie restricted group ate at 8am , 1pm and 8 pm. Between the two groups the intermittent fasting group lost a little bit more fat than the calorie restricted group, while strength and muscle mass remained the same (both groups increased muscle mass) .
What can we conclude from these studies? Simply put, there is not a lot of research to prove that fasting will cause muscle loss. One need not be fearfully of trying out intermittent fasting given its plethora of benefits. However, adherence and sustainability is the key. If you can adhere to intermittent fasting for a longer period and make it your lifestyle you will be benefited more than individuals who do it for a short period of time.