Note : This article is NOT a substitute to advice of a doctor for health conditions. Please take advice of your doctor for any medical conditions. People with diabetes need to work with their doctors to adjust their medication accordingly during fasting to prevent hypoglycemia. Pregnant and breastfeeding women are not advised to do any form of fasting.
Whether you are a health conscious person or someone looking for weight loss options, you certainly would have heard the term Intermittent Fasting (IF)
In simple words intermittent fasting (IF) is clearly demarcating the eating period in a day, so that the reminder of the day becomes the fasting period. Each one of us is doing some form of intermittent fasting. For example if you have breakfast at 6 am and dinner at 10 pm, you would be doing an 8:16 intermittent fasting, which means you fast for 8 hours in a day (mostly during sleep) and eat all your food in a 16 hour window. If you are wondering why it is not helping you lose weight, it’s all about increasing the fasting window and decreasing the eating window. So 16:8 is what would probably be beneficial. Now let’s look at the science behind this act.
Most modern lifestyle diseases like obesity and diabetes are governed by the action of a hormone called insulin, which is a anabolic (building) hormone. Insulin does the work of regulating your blood glucose by storing it in liver, muscle and fat cells. So it essentially builds reserves of glycogen and fat. In an ideal scenario if we eat the exact amount of calories that our body needs to maintain our daily lifestyle, most of the glucose is stored in the liver (as glycogen) and muscle. This storage would be used up as we carry out our routine and then we burn fat. This would be a state in which we maintain our weight. However most of us consume far more calories than we need and do it for prolonged periods of the day (midnight snacks!). This results in insulin being active most of the day and as it’s anabolic it drives storage.
The other set of hormones which are important in this discussion are a group of hormones called counter regulatory hormones namely glucagon (breaks glycogen), growth hormone, cortisol and adrenaline. These hormones are catabolic (breaking) and help us burn the glycogen, and fat, in the event of exhaustion of glycogen reserves (fat burning is what we need for weight loss). Now the counter regulatory hormones can’t do their work till insulin is given some rest. So the whole logic of intermittent fasting is that we give a clear instruction to our hormones whether you want the building or breaking mode to be ON and for how long. If you are fasting for most time of the day, the counter regulatory hormones start breaking the reserves for energy. Alternatively if you are eating for most of the day, insulin will keep building your reserves and thus making you gain weight. In the extreme case one will become insulin resistant leading to increased blood sugar levels, commonly called as DIABETES!
Types of Intermittent Fasting
In this type of IF you eat for 12 hours of the day and fast for the remaining 12 hours. An example of this would be having your breakfast at 8 am and finish dinner by 8pm. All the meals that you eat would be within the 12 hour window of 8am to 8 pm. This is the most basic form of IF and helps maintain the weight, if we are eating the right amount of calories as per our energy needs.
This is the most common form of IF and is known to have weight loss benefits. Essentially you are in breaking mode for a longer period than the building mode. An example of this would having your first meal at 12pm and having the last meal at 8pm. Another option would be having breakfast at 8am and last meal at 4pm. 16:8 generally involves skipping one meal, either breakfast or dinner.
This is an extreme form of IF in which all the meals are consumed within a 4 hour period of the day. Also called as the warrior diet, this is inspired by the warriors who would consume all their meals in the evening. This would keep one in fat burning mode for most of the day.
24 hour fast
This involves eating only one meal a day. For example if you have dinner at 7pm today, you would not have any meal till the next day 7pm.
This form of IF involves eating normally for 5 days if the week and consuming minimal calories (around 500) for the remaining two days.
Alternate day fasting (ADF) involves eating normally every alternate day and eating in a restricted way in the other days.
How to choose which method?
As you can see there are different forms of IF and some times all this jargon could confuse people. So here are few tips on how to choose. Like any other health intervention two things are major deciding factors, your current state of health and your target state of health.
1. If you are a healthy individual with ideal body weight and body fat percentage, a 12:12 would help you maintain the body function in a good way. It will also increase insulin sensitivity preventing any lifestyle diseases in the future.
2. If you are borderline obese and have a need to lose body fat to be more healthy, 16:8 would be a good point to start. As this involves skipping one meal, it will result in a caloric deficit aiding in weight loss. Further the 16 hour fasting window gives the body a chance to burn fat post exhaustion of glycogen reserves. The best part about this form is that it would not disrupt your social life, especially if you are skipping your breakfast.
3. If you are grossly overweight and have problems with carrying out your daily activities, you could do the much difficult forms like 20:4 or the 24 hour fast. If you are totally new to fasting i would suggest to start with a 16:8 and start understanding the basics before you progress to more intense forms. However i would not advice being in this state for a long period as it could result in reduction of metabolic rate. As you achieve your goal you should gradually shift to milder versions like 16:8 and 12:12
4. If you are opting for a 5:2 fast, i would advice not to club the fasting days. Spread them over the week. For example if wednesday is your first fasting day, let the next fasting day be a saturday. Prolonged fasting is a very complex act and could create electrolyte imbalances.
5. ADF and 5:2 are know to cause lot of hunger and brain fog in some cases. So i personally avoid these formats.
Finally its important to understand that fasting is not a substitute to eating bad food during the non fasting periods. There is no substitute to eating healthy. Always prefer seasonal, local and whole foods.