The latest diet trend, which is eating twice a day and fasting the rest of the time, or what is more generally called as “Intermittent Fasting”(IF) is quite in vogue now a days. Just like the other trends such as keto diet, GM diet, Detox, 5:2 this one too has a little bit of science and a lot of hype surrounding it.

Lets try to understand this beyond the hype. Although IF is followed with multiple patterns (Weekly fasting, Daily Fasting, Single food-window per day etc) the one currently in craze is the two-meals-a-day pattern. So I’ll only address that for now.

About Insulin

Before we get into this, we need to know a little bit about insulin.

Insulin is a hormone released by the pancreas to control blood-sugar levels. Why? Because when our digestion starts, and especially when we eat high-sugar foods, blood sugar levels start rising rapidly, and if not controlled, these levels could prove to be fatal. Thus the body releases insulin, which triggers storage of this sugar as glycogen and fats, reducing the blood-sugar level. Once the blood-sugar levels are low, the secretion of insulin stops. As long as insulin is in the blood our body does not burn fats stored in fat cells.

Eating food within 50 minutes will stop the body from secreting more insulin, is not exactly true.

Insulin secretion is not so cut and dried. There are multiple factors to it.

How much insulin is secreted at the start of a meal is dependent on how much was needed the last time, so if you eat low GI foods primarily the insulin secretion is lowered in general. Even thinking of food or seeing/smelling it will cause some release of insulin, called cephalic phase insulin release.

Also, if you eat some food which has enough glucose in it such that the first release of insulin does not lower the blood sugar, the pancreas WILL release additional insulin to control it, regardless of how quickly you gulp it.

The amount of insulin released is related to how much glucose is in the blood, which is directly related to WHAT is being eaten. The 50 minute effect primarily helps in controlling food intake rather than exact insulin secretion. As you can only eat so much food in one go.

What does Intermittent Fasting do?

In intermittent fasting, you’re supposed to not consume any food during a long time-window (10 hours or so). During this window, any food that is consumed in the previous meal gets digested, and all the blood sugar rise resulting from it is used up. With the lowering of blood sugars (couple of hours after your meal typically), the body starts using the stored glycogen and fats for energy, which results in fat loss and weight loss.

The primary reason why IF works is simple restriction of calories due to fewer meals and not restriction of insulin secretion. Binging on high-calorie foods even during IF will not make you lose weight.

For some people following IF may be very convenient and sustainable for long term, for others, it may lead to hunger pangs and they’ll end up having less control and eat unhealthy foods during their meals. May also have issues with concentration/stress due to hunger.

What are the problems?

Although theoretically the approach seems right, there are some practical problems when it is followed every day. In simple words, any pattern/diet that is very different from usual routine and from the routines of people around us becomes challenging in the long run.

Nutritional deficiencies

Long hours of fasting may lead to deficiencies of micronutrients and also of proteins in vegetarians. As at one go it becomes difficult to eat the required quantities of all the nutrients and food groups. For example, milk products & citrus fruits or fish & curd. Also, with only two meals, most people tend to prefer roti, dal, subzi, rice. Automatically skipping few important foods like fruits, nuts & oilseeds. A normal eating pattern with balanced diet stresses on including plenty of fruits and salads as a source of fibre, which helps with skin health, constipation and in fat loss.

Issues with meal-time

For many busy people, eating exactly at a given time everyday, especially when that time does not match with a general meal time (like lunch or dinner) becomes very difficult. One may get hungry at 10 am, but being a working professional, may find it hard to eat till noon despite the hunger.

Wrong food choices

When you eat after a long gap, your self-control diminishes a lot, so you are more likely to binge on gratifying foods like fast foods, or desserts. Many people find it difficult to consciously have healthy foods when they are very hungry.

Constant thinking about food

Because of the restriction of food timings, people tend to fixate on food a lot, and spend a lot of time thinking about meal-time and what to eat.

Discomfort

Long hours of fasting can lead to hypoglycaemia resulting in dizziness, drowsiness and fainting. In many people, it also triggers acidity and constipation. Constant feeling of hunger also causes mood swings & irritability.

What about nutrition?

Intermittent fasting in reality is not really a diet at all. It is just a pattern, since it makes no comments at all about nutrients and what kind of foods should be had. People with nutritional deficiencies or conditions like anaemia, elevated creatinine/uric acid levels, dyslipidemia etc need to be aware that unlike balanced diet, intermittent fasting by itself will make no difference to their deficiencies/health issues.

Gaining weight back quickly

If you cannot sustain this pattern after a few days, any deviation tends to result in going back to the original weight quite quickly. Since many people doing IF are unaware about calorie intake or making healthy food choices (as they are banking on just the pattern to lose weight), weight gain becomes almost inevitable after failing to follow the pattern.

Conclusion

For someone who can sustainably eat only two meals a day without compromising on the quality of food and manage cravings and schedules, especially consuming enough fruits, vegetables for their fibre and vitamin requirements, the pattern may help. But it cause significant friction in regular life for many.

Rather than fixating on weight loss, and hunting for tricks and short-cuts to weight loss, try to focus on achieving good health through nutrition, for which there are no short-cuts. Healthy, balanced and sustainable diet is the key to your well-being.

References

• Smeets, PA; Erkner, A; de Graaf, C (November 2010). “Cephalic phase responses and appetite”. Nutrition Reviews. 68 (11): 643–55. doi:10.1111/j.1753–4887.2010.00334.x. PMID 20961295.
• Wilcox G. “Insulin and Insulin Resistance”. Clin Biochem Rev. 2005 May; 26(2): 19–39. PMID: 16278749