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

Intermittent fasting is a popular eating pattern that alternates 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 certain days of the week. Many people find these types of plans appealing 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 nonfasting). 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 beverages, such as black coffee or tea, 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).

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 on 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 for 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.

Metabolic switching may improve metabolism, resulting in greater weight loss. Besides weight loss, metabolic switching may also increase health span and longevity.

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 reduce the calories consumed.

Combining a time-restricted eating schedule with a reduced-calorie intake might be effective for weight loss. However, such specifics need more research.

Common side effects with intermittent fasting:

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

Additional 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.

Safety issues with intermittent fasting

Ideally, your provider will monitor 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

Considerations with intermittent fasting

Any diet should be sustainable for the long term. Yo-yo dieting or weight cycling is associated with worse health outcomes, including an increased risk of developing type 2 diabetes.

When deciding whether intermittent fasting is right for you for weight loss, consider its impact on your social life and routine. Social activities, exercise, and time with loved ones are other essential components of health. Ignoring these activities because of your eating window may not have a net positive benefit on weight loss.

It is important to not consider your eating window a time to consume any and all foods. A balanced diet and limiting overindulgence are still central to successful weight loss.

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 intentional fasting periods

Mark a day as complete

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

Use the Intermittent Fasting tracker

MyNetDiary offers a ready-to-go tracker for intermittent fasting. Go to the “Coach” tab, then select “Intermittent Fasting.”

The calendar lets you track and monitor your IF routine.

Tap “Add Fast” to enter your fasting details.

Choose from different common fasting patterns, or manually enter your fasting details.

Key takeaways

• Intermittent fasting may be the right approach to support weight loss as long as you are a healthy, overweight adult who tolerates hunger well.
• Condensing your eating window each day or each week may lead to less temptation to snack, contributing to eating less and losing weight.
• Besides modest weight loss, you may also see improvements in insulin sensitivity, cardiometabolic factors, and other indicators.
• Tracking in MyNetDiary allows you to gauge how intermittent fasting is impacting your nutrition. Review Nutrition Highlights under your Weekly Analysis to detect any nutrient gaps.

Before starting intermittent fasting, talk to your doctor, particularly 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 true

Updated by Amy Brownstein, MS, RDN on September 26, 2025

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Weight Loss->Diets