The quest for perfect health and a long life has always driven humankind to try different kinds of food and diets. Despite all the advances in science, the search for an ideal diet remains elusive. For centuries, the fight was to get enough food to survive till cereal cultivation allowed humans to survive without having to always hunt for their food. However, the progressive, widespread availability of energy-dense, carbohydrate-rich food based on refined cereals has resulted in an epidemic of obesity and non-communicable diseases like diabetes and heart diseases.
The search for a diet to help us lose weight and reduce our risk of non-communicable diseases has led to the popularity of many dietary fads and fashions. Atkins diet, Paleo diet, South beach diet, GM diets are examples that have come and gone. Similarly, a diet pattern that has gained immense popularity in the last few years is intermittent fasting.
Intermittent fasting may work in cases but no data suggest that it is a miraculous path to good health and longevity. Besides, it is not for everybody, says Dr Ambrish Mithal, Chairman and Head, Endocrinology and Diabetes, Max Healthcare.
What is intermittent fasting?
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Fasting has been practised from time immemorial as a means to cleanse one’s body and has been recommended by most religions, albeit in different forms. Intermittent fasting essentially means periods of fasting followed by periods in which eating is permitted. There are several methods of practising IF. Alternate day fasting entails restricting your food intake to 500 calories every alternate day while following your usual calorie routine on other days. One could also fast twice a week (5:2 method), or five days every month. The most popular variant of IF, in India, is however, the 16:8 method. In a 24-hour cycle, this requires fasting for 16 hours and allows free food consumption in the remaining eight hours.
How is intermittent fasting thought to work?
The basic difference between intermittent fasting and simple calorie restriction is that our bodies tend to adapt to low calorie intakes over a period of time. As a result, we stop losing weight after three to six months despite persisting with a low-calorie intake. It is thought that allowing “normal” food intake intermittently is able to keep the body responsive to changes in diet.
What happens to our metabolism when we fast?
Whenever we eat food, there is a rise in blood glucose levels and some fats in our bodies. This leads to a surge of insulin which facilitates the uptake of these substances and utilisation by the cells. When glucose supply exceeds energy intake, it is stored as glycogen and ultimately as fat in our body. When we fast, there is a lack of glucose, so energy supply to tissues like muscle, heart, liver and kidneys is maintained first by glycogen and then by breaking down stored fats into ketones (metabolic switch).
Ultimately, when we fast for prolonged periods, our body fat stores start melting. It has also been suggested that intermittent fasting may help in cell repair (which may combat ageing) and produce favourable effects on metabolic parameters like cholesterol and blood sugar. Animal studies suggest major benefits of fasting, including longevity.
Does this mean that intermittent fasting is the ultimate solution to obesity, diabetes and heart disease conditions?
Human studies have shown that intermittent fasting typically produces weight loss of three to five kilos over two to three months, although there is wide variability in the results. Unfortunately, for the proponents of intermittent fasting, most studies have not shown a significant benefit of intermittent fasting over other approaches in terms of weight loss, lipid parameters, blood glucose levels and others. The impact of intermittent fasting in these short to medium-term studies could largely be attributed to a reduction in calorie intake. For comparable calorie intakes, conventional calorie restriction was as effective as intermittent fasting in improving metabolic parameters.
Where does that leave us with regard to the current status of intermittent fasting?
Intermittent fasting is an effective weight loss strategy but the data till now suggests that it may not be more effective than calorie restriction by other means. It is possible that intermittent fasting has long-term benefits in humans but the evidence to prove that is not available at present.
I believe that the present use of intermittent fasting is determined by individual choice. Some may find it easy to control their calories by fasting. Others may find it impossible to fast for 16 hours, particularly if they have some chronic health conditions.
Avoiding unhealthy food during the eating period is important, else it can attenuate the benefits of intermittent fasting. The best time to eat is from 8 am to 4 pm, or thereabouts. Therefore, giving up dinner is the best strategy. Giving up breakfast, as many do, is not the best option.
Who should not opt for intermittent fasting?
Pregnant and lactating women, and children should not consider intermittent fasting. Those with diabetes or on medicines that do not produce a low blood sugar reaction (metformin, gliptins, gliflozins) can consider fasting if they want to. Those who get “acidity” when they miss meals are also not the best candidates for intermittent fasting. If you are considering opting for intermittent fasting, connect with your doctor first.
Is intermittent fasting the miraculous path to good health and longevity that we were all waiting for?
The answer is still awaited.