What is intermittent fasting?
It may be helpful to think of intermittent fasting as a lifestyle choice rather than a diet. It doesn't specify which foods you should eat, but rather when you should eat them. Intermittent fasting is the term used to describe several different approaches to short-term abstention from food to improve health. Note the emphasis on 'short-term'; it does not involve fasting for prolonged periods. In summary, intermittent fasting is an eating pattern that cycles between periods of fasting and eating. It is currently very popular in the health and fitness community.
The history
Our ancestors didn't have access to food 24/7 the way we generally do today. They often went for what we would consider long periods without anything to eat, for example, if a hunt was not successful. As a result, humans evolved to be able to function without food for extended periods.
Different types of intermittent fasting
Note that for all types of intermittent fasting, it's important to stay well hydrated. You need to drink adequate amounts of water (or other non-caloric beverage with no sweetener of any kind, e.g. tea) if you're fasting.
Time-restricted eating
For time-restricted eating, you shrink the window of time during which you eat each day. That usually involves extending the duration of your regular overnight fast, to anywhere from 12 to 16 and even 20 hours. This may involve skipping either breakfast or dinner. However, you can choose to have three full meals within a compressed period.
A popular version of this approach is the 16:8 diet, meaning that you fast for 16 hours and compress your eating into eight hours.
However, if this seems too extreme to you, you can still benefit from a less restricted schedule, e.g. 14:10 where you fast for 14 hours and can eat over ten hours. A minimal time restriction would be 12:12, which may be a good starting point if this is a change from your current eating pattern. You could gradually increase the hours during which you fast as you adjust to the changes.
Whole day fasts
One day fasts:
Whole day fasts are just as they sound - fasting for 24 hours as little as once or twice a month or as much as once or twice per week.
A 24-hour fast can start after a regular day of eating, with dinner finishing at 8 p.m. Then you don't eat until 8 p.m. the following day. If you can only manage 18, 20 or 22 hours of fasting, that's still a good start. This isn't an "all or nothing" situation.
Fasting two days per week:
A common pattern of fasting is the 5:2 fasting plan, eating normally for 5 days a week and fasting for 2 (not necessarily consecutive) days. Some people recommend a partial fast, eating small amounts on the fasting days - 500 calories for women and 600 for men.
Fasting for more than two days in a week:
You can increase fasting to 3 days per week and then go to 5 days per week, i.e. 2:5. You would only fast 5 days per week intermittently, e.g. you might consider doing a 'spring cleaning' 5-day fast, and perhaps another one in the fall.
What foods are best to eat on an intermittent fasting diet?
No diet or eating plan will be good for your health if it includes a lot of junk food - added sugars, refined carbohydrates, and processed foods. Equally, physical activity is essential for good health.
Apart from that, the usual recommendations apply: eat lots of vegetables and fruits, as well as whole grains - organic if possible. If you eat meat, do so sparingly, and opt for good quality, such as grass-fed beef, free-range poultry and organic eggs, etc. Wild-caught fish or seafood is better than farmed.
Benefits of intermittent fasting
A major benefit of intermittent fasting is that it helps to lower insulin levels. A 12-hour overnight fast is enough to lower insulin levels because it takes 12 hours of not eating for the body to clear its stores of glycogen (stored sugar) in the liver.
Intermittent fasting can help you lose weight and belly fat without having to consciously restrict calories. It can also help you keep weight off over the long term. Losing weight, moving more, and eating a healthy diet can make you more insulin-sensitive and can help avoid developing type 2 diabetes.
Fasting shifts your body from burning glucose for fuel to using fat stores. During this process, fat is converted to ketones, a more efficient energy source.
Fasting can reduce inflammation, a key driver of many chronic diseases. Fasting has been shown in some studies to lower inflammation markers.
Heart health: Intermittent fasting may reduce "bad" LDL cholesterol, blood triglycerides, blood sugar and insulin resistance - all risk factors for heart disease.
Fasting seems to cause cells to initiate a waste-removal process called autophagy. During autophagy, the body eliminates dysfunctional, damaged cells, to make room for new healthy ones. Autophagy may offer protection against diseases like cancer and dementia.
Intermittent fasting may increase longevity, slow down the aging process and help prevent and treat diseases.
Following a time-restricted approach to intermittent fasting may help regulate circadian rhythms and improve metabolism. Science suggests harmonizing our eating patterns with our biological clocks can lead to improved weight regulation and reduced obesity.
Intermittent fasting doesn't have to feel like a diet. You can choose which version of intermittent fasting works for you so that you can eat what you want within a certain window of time that suits your body and your schedule.
Safety and side effects
Hunger is the main side effect of intermittent fasting. You may also feel weak, and you may not perform mentally as well as you're used to. These side effects may be temporary since it can take time to adjust to your new meal schedule.
If you have a medical condition, you should consult a health professional before trying intermittent fasting. This is especially important if you:
- have diabetes
- have problems with blood sugar regulation
- have low blood pressure
- take medications
- have a history of eating disorders
- are a woman who is trying to conceive
- are a woman with a history of amenorrhea (skipped periods)
- are pregnant or breastfeeding
- have hormonal imbalances
- are under a lot of stress
- are suffering from chronic fatigue
However, there is nothing dangerous about not eating for a while if you are healthy and well-nourished overall. Remember, you can ease your way into intermittent fasting, e.g. start with a shorter fasting period and gradually increase it as you adjust to the changes in your eating pattern.
I offer a 7-week program to help people learn to fast properly. I give classes week by week and educate participants so they can fast successfully and avoid the misguided information on fasting that is so easy to find.
I hope you find this information helpful and can see that intermittent fasting can involve minimal change to your routine if you try a time-restricted plan. The health benefits are substantial without major disruption of your schedule - worth a try unless your health indicates otherwise.
