Intermittent fasting has taken over headlines and become one of the most popular diet fads. What is intermittent fasting? Should you follow it? How do you do it? Here are some FAQs on intermittent fasting, often referred to as “IF,” and some answers. As with any diet program, be sure to ask your healthcare provider before trying intermittent fasting.
Intermittent fasting is an approach to weight loss and blood sugar control that involves fasting or severely restricting calories during some hours or days, and eating normally at other times. It can help you reduce your food intake without strict calorie or carb counting.
Intermittent fasting works for weight loss by limiting your calorie intake relative to your calorie expenditure, or output. That’s how any weight loss diet works. The difference with IF is that the emphasis is not on what you eat, but on when you eat. The idea is that by limiting the time periods during which you eat, you end up eating less overall.
With regards to health benefits, some of the benefits come from losing weight. Other benefits may be hormonal and linked to the periods you go without eating or with a severe calorie deficit. There can also be some effects of going without high amounts of carbohydrates for long periods of time, since that can shift your metabolism and also change the balance of some of your hormones.
There are a few different approaches to intermittent fasting. They all rely on setting times when you can and cannot eat. Some common methods are the 16:8 method, the alternate day method, and the 5:2 method. If you want to try IF, ask your doctor which may be best for you. You can also consider which may fit best into your lifestyle.
The 16:8 method involves letting you eat during an 8-hour window during the day. The other 16 hours, you do not eat. For example, your window of eating might be from 10:00 a.m. to 6:00 p.m., which would mean your window of fasting (not eating) would be from 6:00 p.m. to 10:00 a.m. Or, you might choose to have your window of eating from noon to 8:00 p.m. and your fasting period from 8:00 p.m. to noon.
The alternate day method lets you eat normally on alternate days, and a very low calorie amount on “fasting” days. While you may not actually be fasting on your “fasting” days, the calories might be as low as 400 to 600 for the entire day.
With the 5:2 method, you eat normally, in moderate and healthy amounts, for five days of the week. Select 2 non-consecutive days that will be your “fasting” days, and consume only 400 to 500 calories on those days. By restricting your calories so much on those days, you can lose weight.
Like any diet, intermittent fasting only works if you follow it. Once you and your healthcare provider decide on the rules about what to eat and when to eat it, it’s up to you to follow it so that you see the results you want.
As with other diet programs, it will only work if you don’t eat around it. For example, if you are following a 16:8 program and you overeat during the 8 hours that you are allowed to eat, you won’t lose weight. Instead, it’s best to have a reasonable amount of healthy foods, in pre-planned meals or snacks, during your non-fasting periods.
Intermittent fasting can help with weight loss by limiting calorie intake. It may also help reduce insulin resistance in prediabetes, which is a risk factor for type 2 diabetes, again by limiting calorie intake. It’s possible that IF can help improve cholesterol levels and triglycerides if you follow it properly and choose healthy foods.
Some people have asked about longevity and intermittent fasting. It seems as though calorie restriction may help boost lifespan, but it’s unclear whether IF can do the same.
Other benefits of intermittent fasting are the same as benefits related to weight loss. They can include the following.
- Decreased inflammation.
- Increased energy.
- Lower blood pressure.
- Better sleep.
If you feel okay and your doctor says it’s okay, you can exercise on your fasting days as well as on your eating days. At best, you can burn extra fat during fasting periods since your body won’t have as much carbohydrate stored up.
However, you may feel less energetic on your fasting days or during your fasting periods. And don’t expect to set a personal best or win a competition while fasting. Be sure to let your body dictate how intense your workout is, and drink plenty of water, and possibly electrolytes, to replace losses from sweat and from fasting.
Intermittent fasting doesn’t focus on which foods you eat, but your food choices are always important. To lose weight and be as healthy as possible, it’s best to choose foods that are the following.
- High in nutrients, such as protein and dietary fiber.
- Less processed.
- Low in added sugars and refined starches.
- Low in saturated fats.
Fruits, vegetables, lean proteins, beans, nuts, and low-fat dairy products are generally good choices.
There are some foods that can get in the way of weight loss because they’re high in calories and not very filling. Even on your higher-calorie days or during your “eating” periods, it’s best to limit foods such as sweets, fried foods, fatty meats, fatty foods, and highly processed refined carbs.
Yes, you should drink a lot of water when you are following intermittent fasting. That’s important during your fasting periods and your eating periods. Along with keeping hydrated, drinking more water can help prevent constipation and headaches, which are both possible side effects of intermittent fasting. And, there’s more good news. Drinking more water is associated with increased amounts of weight loss!
Intermittent fasting can be safe for many people without medical conditions. Whether or not you have medical conditions, it’s best to ask your doctor about it before you start it. Be sure to bring up any medications you are taking and any other health concerns you may have.
Being hungry is a natural side effect of going so long without eating or with eating a very low amount of calories. Related to this may be feeling tired and weak, or having less energy. Migraines, confusion, and nausea are also possible side effects. Constipation can also result. Talk to your doctor if you have concerns.
People with type 1 diabetes and people with type 2 diabetes who are on insulin shouldn’t try IF. It can lead to hypoglycemia if you are on insulin or sulfonylureas medications. These are other groups who shouldn’t try IF.
- People who are underweight and shouldn’t lose weight.
- People with high blood pressure or heart conditions.
- Women who are pregnant or breastfeeding.
- People under age 18. Their hunger cues may still be developing and it may not be safe to do IF.
- People who have a history of eating disorders.
If you have any doubts at all, it’s best to bring them up with a healthcare provider. It’s possible that IF isn’t safe for you, but it’s possible that it could be okay with supervision.
A common concern with low-calorie diets and weight loss is that metabolism can slow. Your metabolism is the rate at which your body burns calories. A reduced metabolism can lead to more trouble losing weight. There isn’t substantial evidence supporting slower metabolism on IF compared to other weight loss diets. Some proponents of intermittent fasting believe that including an occasional period of higher-calorie intake can support a higher metabolism.
This is a tough one, but it gets easier! The best advice may be to just be patient. Your body may take a while to get used to intermittent fasting, and your mind may take a while to do so, too. In the meantime, you can choose a method that is easiest for you. Some people believe the 16:8 method doesn’t make them feel as hungry.
As long as your doctor says it’s okay and you feel okay with it, intermittent fasting is sustainable. It’s flexible in terms of which foods you can eat, so you can add in treats if you have cravings or want to eat special foods for holidays or other events. And, you can plan ahead to make sure that parties, restaurant outings, and other special eating occasions fall during your eating periods instead of your fasting periods.