Does intermittent fasting work for weight loss, and what should I know first?

Intermittent fasting is a popular type of eating pattern that cycles between periods of eating and not eating and is touted for weight loss. The plan centers around when to eat instead of what to eat.

Some research shows intermittent fasting may be as effective for weight loss as traditional dieting on fewer calories. Read on to learn about the most popular time-restricted eating plans, benefits, and considerations.

What is intermittent fasting, and how might it help your weight loss?

Intermittent fasting is just as it sounds–you eat only during specific hours of the day or specific days of the week. Many people are attracted to these types of plans to help place limits on eating times, control appetite, and ultimately lose weight.

Intermittent fasting features two main categories: whole-day fasting and time-restricted eating.

Time-restricted eating

The most popular type of time-restricted eating is the 16:8 plan, 16 hours of fasting followed by 8 hours of nonfasting.

A more flexible approach is the 12:12 (12 hours fasting and 12 hours non-fasting). For example: if you finish dinner at 6 PM on Monday, your next meal/snack is no earlier than 6 AM the next day.

A stricter version of time-restricted eating is the 23:1 plan. This includes eating one meal per day, followed by 23 hours of fasting.

All plans allow water and other non-caloric beverage consumption during the fasting period.

No matter what eating window you follow, the ability to share at least one meal a day with family and friends is a benefit of time-restricted eating.

Whole-day fasting on certain days of the week.

The most popular type of whole-day fasting is the 5:2 approach, 5 days of nonfasting followed by 2 days of fasting or a modified fast eating only 500-600 calories. Intermittent fasting plans that call for 2-3 days per week of fasting (or eating very little) are hard for many individuals to sustain over the long term. Nevertheless, some people can stick to this type of intermittent fasting and have success with weight loss.

Alternate-day fasting (ADF)

Alternate-day fasting (ADF) consists of a “fast day” in which you consume between 0-25% of your caloric needs. You then alternate with a “fed day,” in which you eat your normal diet, thus fasting for 3-4 days a week. Typically, this plan results in greater weight loss than time-restricted feeding (see below).

Other benefits of time-restricted eating or intermittent fasting

In addition to weight loss, researchers are exploring intermittent fasting for other health benefits, including improved insulin sensitivity, reduction in blood pressure, and cell health.

What does the research show regarding weight loss?

The 3 most common types of intermittent fasting showed the following results over the short term (8-12 weeks).

Time-restricted eating: Modest weight loss of 3-4%. For a 175-pound person, this translates to a weight loss of 5-7 pounds.

5:2 plan: 4-8% loss

Alternate-day fasting (ADF): 4-8% weight loss

These results are similar to more traditional diets that promote daily calorie restriction.

Longer-term studies

Research looking at the longer-term impact of ADF and the 5:2 diet on weight loss (24-52 weeks) does not indicate greater body-weight reductions than in short-term studies.

Some investigators hypothesize that the weight-loss efficacy of these eating plans may peak at 12 weeks.

How might intermittent fasting result in weight loss?

Fasting a certain number of hours each day or days per week might help your body burn fat. After your body has gone hours without food, it exhausts its glycogen or sugar stores and starts to burn fatty acids or ketones for fuel. This is sometimes referred to as metabolic switching.

Some people feel more in control of what they eat if they limit their daily eating window. This can be especially helpful if you snack a lot in the evenings. By limiting your eating hours, you will cut down on calories consumed.

Combining a time-restricted eating schedule with a reduced-calorie intake might be effective for weight loss. However, more research is needed in this area.

You may experience these side effects with intermittent fasting

• Decreased energy
• Hunger-related symptoms
• Low blood sugar
• Bad breath
• Headaches
• Irritability

Safety issues with intermittent fasting and weight loss

Ideally, your provider will be monitoring these metrics during your first 3 months of intermittent fasting:

• Electrolytes
• Vitamin D
• B12
• Blood pressure and blood pressure medication
• Blood sugar and blood sugar medication

Intermittent fasting for weight loss is not recommended for:

• People with a history of an eating disorder
• People at risk of developing an eating disorder
• Underweight adults with a BMI <18.5
• Children
• Women who are pregnant or breastfeeding
• People who have had weight-loss surgery (bariatric surgery)
• Anyone with a high risk for hypoglycemia (low blood glucose), such as individuals taking daily insulin or sulfonylurea
• Anyone who has hypoglycemia unawareness, meaning their blood sugar decreases, though they can’t always feel it.

Note: Teens and individuals over 70 should check with their doctor before trying intermittent fasting for weight loss.

How to use MyNetDiary during intermittent fasting

MyNetDiary has two helpful features for when you intentionally do not eat.

Mark a day as complete

If you are eating less or doing a modified fast, mark your day as complete to ensure your analysis includes these days.

Fasting hours custom tracker

Keep track of your eating and fasting windows by creating custom trackers.

The bottom line

Losing weight and keeping it off is a challenging task. Intermittent fasting may be the right approach to support weight loss if you are an otherwise healthy, overweight adult who seems to tolerate hunger well.

By condensing your eating window each day or each week, you may be less tempted to snack, which can help with eating less and losing weight.

In addition to losing a modest amount of weight, you may also see improvements in insulin sensitivity, cardiometabolic factors, etc.

By tracking in MyNetDiary, you can guage how intermittent fasting is impacting your nutrition. By reviewing the Nutrition Highlights under your Weekly Analysis, you’ll be able to detect any nutrient gaps.

Finally, various diets and eating patterns impact people differently, so talk to your doctor if you are at risk of low blood sugar or experience headaches, unusual anxiety, nausea, or any new signs and symptoms.

Related content

What to eat during intermittent fasting when you socialize

Soothe yourself without food. What to do instead of eating

What popular fad diets are safe? How to tell if your weight-loss plan is too good to be true

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Weight Loss->Diets