Intermittent fasting refers to eating plans that alternate between fasting and eating periods. The goal is to systematically starve the body long enough to trigger fat burning. While research is still underway and the method may not be suitable for everyone, there is evidence that, when done correctly, intermittent fasting can help lose weight, lower blood pressure and cholesterol, prevent or control diabetes, and improve brain’s health.
During a meal, carbohydrates in food are broken down into glucose. Glucose absorbs through the intestinal wall into the bloodstream and is transported to various organs, where it serves as the major energy source. Excess glucose is stored for later use in the liver and dispose tissue, in the form of glycogen and fats. In between meals, when the body is in the fasted state, the liver converts glycogen back to glucose to keep supplying the body with energy.
Typically, an incentive person takes about 10 to 12 hours to use up the glycogen stores, although someone who exercises may do so in much less time. Once the reserves of glycogen in the liver is depleted, the body taps into energy stores in adipose tissues. This is when fats are broken down into free fatty acids which are then converted into additional metabolic fuel in the liver. Thus, if the fasted state lasts long enough, the body burns fat for energy and loses that extra fat.
Insulin is the hormone required for driving glucose into cells. Insulin level is regulated to match the amount of glucose in the blood, that is, high after a meal and low between meals. Because insulin is secreted after each meal, eating throughout the day keeps insulin levels high most of the time. Constant high insulin levels may de-sensitize body tissues, causing insulin insensitivity – the hallmark of prediabetes and diabetes type 2.
Fasting helps keep insulin levels low, reducing diabetes risks. Fasting also has beneficial effect on the brain. It challenges the brain the same way physical or cognitive exercise does. It promotes production of neurotrophic factors which support the growth and survival of neurons.
Fasting, however, is not for everyone. Among those who should not attempt fasting are:
- Children and teens
- Pregnant or breastfeeding women
- People with eating disorders (anorexia, bulimia …)
- Diabetes type 1, advanced diabetes
- People with some other medical problems
- People who are underweight or frail
Fasting can also be unsafe if overdone, or if not done correctly. There are several approaches to intermittent fasting, but the easiest way to achieve is perhaps the one that simply extends the usual nighttime fast. A daily cycle of 16-hours fast followed by a 8-hours eating window is usually sustainable.
Tips for Safe and Effective Fasting
- For intermittent fasting to be safe and effective it must be combined with balanced meals that provide good nutrition.
- It is important to stay hydrated (drink plain water during fast)
- Do not exercise excessively, know your physical limits while fasting.
- Break your fast slowly
- Overeating after fast, especially of unhealthy foods, must be avoided.