As a weight loss doctor, I have patients ask me about fasting all the time. And it’s no wonder because information about fasting is everywhere. You see it on social media, hear about it on podcasts, and it always seems like an amazing before-and-after transformation story. Some people do lose weight with fasting, but weight loss usually comes from an overall calorie reduction. Fasting can be a tool for some patients, but it should be used safely and with caution.
Fasting has grown in popularity over the years, but there are a few different ways people choose to do it. The most common type among dieters is intermittent fasting, avoiding food for structured fasting periods. Other common types are time-restricted eating within a set window during the day and extended fasting, which is fasting more than 24 hours at a time. Although it sounds strict, fasting should not mean ignoring hunger, dehydration or medication needs.
While fasting is not a magic cure for weight loss, it can help people who have mindless eating habits, such as late-night snacking and grazing behaviors. It can also reduce intake of ultra-processed foods that are commonly consumed between meals. For some, it helps improve awareness of true hunger versus eating out of habit or stress eating. Fasting works best when the eating window is still focused on nutritious, balanced meals.
While some people do see results from fasting, you need to consider whether it’s safe. A 12-hour overnight fast, such as 7 p.m. to 7 a.m., might be the best option if you want to try fasting in a sustainable way. From here, if you feel like it may help, you could consider gradually shortening the eating window only if it feels sustainable and does not trigger overeating, dizziness or disordered eating patterns. If you want to fast, start gently rather than jumping into extreme fasting plans.
Keep in mind that these guidelines are based on a generally healthy person. Certain medications and conditions are not compatible with fasting. You should talk to your doctor before considering a fasting plan. After bariatric surgery, fasting can be unsafe because of your unique nutrition requirements and the risks associated with not getting the nutrients you need when you need them.
Most people see benefits from more conservative dieting options than fasting. Fasting does come with risks, especially if you have pre-existing conditions. These are some warning signs that you should stop fasting and seek medical attention:
Remember, fasting is an option, not a requirement, for weight loss. If you’re looking to lose weight, start with the basics: stop sugary drinks, reduce processed foods, and build nutrient-dense meals. What works for one person may be unsafe or unsustainable for another. If you consistently reach your nutritional goals, exercise regularly, and still cannot seem to lose weight, consider reaching out to your doctor for further guidance.
