Fad Diet Series: The Werewolf Diet (Does the Lunar Diet Work?)

Medically reviewed by Dr. Angela Tran, DO, double board-certified in Internal Medicine and Obesity Medicine · Originally published 2014 · Updated October 15, 2026

The Werewolf Diet is a fad diet that combines research on intermittent fasting with long-time superstition and a dash of postmodern hokum to claim that you might be able to lose up to 6 pounds in a day. Actual evidence that it works for weight loss is lacking.

How does the werewolf diet work?

The Werewolf Diet is like a cleanse diet, but it is meant to be repeated for long periods. During the new and full phases of the moon, about twice a month, you are supposed to fast or cleanse for one to three days (some versions say as many as six). Most of the time the cleanse is a variation on the cabbage soup diet: vegetable broths, juices and the like. Between moons, some versions add rules such as eating less while the moon is waxing and not eating after 6 p.m.

The reasons given for timing your fasts to the moon are twofold. First, there’s the age-old superstition that our minds and bodies are tied to the phases of the moon. Before artificial light, the moon may have shaped some human habits, but there’s little evidence that this connection survives today, or that it affects mood, appetite or metabolism.

Second, promoters claim that because the Moon creates ocean tides, it also pulls on the water in your body, so fasting on a full or new moon helps you “flush” water and fat. This is where the diet goes from unproven to impossible.

Does the moon pull water out of your body? No

Ocean tides happen because the Moon pulls a little harder on the side of the Earth facing it than on the far side, and the Earth is about 7,900 miles wide. Across a body that’s 5 or 6 feet tall, that difference is vanishingly small: physicists put it at less than a trillionth of Earth’s own gravity. The Moon’s pull also depends on its distance, not on whether it looks full or new. Your body’s water is held inside cells and blood vessels and doesn’t “tide” at all.

Appetite doesn’t follow the moon either. In a 2020 study, 88 adults recorded everything they ate during a new moon and a full moon, and there was no meaningful difference in calories or macronutrients.

Does the werewolf diet work?

As with any calorie reduction, this diet might help you lose weight, if it actually reduces your calories. People tend to overeat after coming off a fast, so it’s quite possible that someone on this diet eats more over the month than someone following a traditional plan.

The “up to 6 pounds in a day” promise is mostly water. Fasting uses up glycogen, the carbohydrate stored in your liver and muscles, and glycogen is stored with water, so the scale drops fast and climbs back just as fast. To lose 6 pounds of actual fat in a day you’d need a deficit of roughly 21,000 calories. There is essentially no research on whether this diet, on the whole, helps with weight loss.

What the research says about intermittent fasting

There is real research on intermittent fasting, and it’s more encouraging than it was when I first wrote this post, but it’s not magic. A 2025 review in The BMJ pooled 99 randomized trials and found that intermittent fasting and everyday calorie restriction produce similar weight loss; alternate-day fasting came out slightly ahead, by about 3 pounds. Some studies show fasting can improve insulin sensitivity, which may help people with prediabetes or type 2 diabetes.

What about the heart? In 2024 an American Heart Association conference abstract linked eating within an 8-hour window to a higher risk of cardiovascular death. That was an observational survey study, not peer reviewed and not proof of cause, but it’s a good reason not to treat fasting as risk-free, especially if you have heart disease, diabetes, or take medications that lower blood sugar.

For science-based weight loss

If you are looking for help with weight loss, Med-Fit Medical Weight Loss can help. We’ll give you science-based recommendations and put you on a doctor-supervised plan that helps you lose weight safely, with or without medication. Compare Med-Fit programs, see how Comprehensive Coaching keeps you accountable week to week, or learn whether GLP-1 medications could help quiet the hunger that makes fasting so hard.

Frequently asked questions

What is the werewolf diet?

The werewolf diet, also called the lunar or moon diet, is a fad plan that has you fast or drink only juice and broth for one to three days around each full and new moon, then eat lightly in between. It became popular in 2014 after celebrity mentions. It is not based on research.

Can you lose 6 pounds in a day on the werewolf diet?

Not 6 pounds of fat. A pound of fat stores roughly 3,500 calories, so losing 6 pounds of fat in a day would take a deficit of about 21,000 calories. What drops quickly during a fast is mostly water and stored glycogen, and it comes back once you eat normally.

Does the full moon affect your weight?

No. The Moon’s pull depends on its distance, not on whether it looks full or new, and its tidal effect across a human body is far too small to move water or fat. A 2020 study of 88 adults also found no difference in how much people ate at the full moon versus the new moon.

Is intermittent fasting good for weight loss?

It can work, but it isn’t magic. A 2025 BMJ review of 99 randomized trials found intermittent fasting and everyday calorie cutting led to similar weight loss, with alternate-day fasting slightly ahead. The best plan is the one you can keep, ideally with medical guidance if you have diabetes or take medication.

Sources

1. U.S. News & World Report. Should you try the werewolf diet? (2014)
2. TIME. Promising the moon: the truth behind the werewolf diet (2014)
3. National Radio Astronomy Observatory. Does the force felt by a person vary with lunar phase?
4. Scientific American. Lunacy and the full moon
5. No effect of lunar cycle on the energy or macronutrient intakes of adults. Proc Nutr Soc 2020
6. Cleveland Clinic. What is a calorie deficit? (early weight loss is often water weight)
7. Prevention. The werewolf diet (calorie math)
8. Intermittent fasting strategies and their effects on body weight: network meta-analysis of 99 randomised trials. BMJ 2025
9. Sutton EF, et al. Early time-restricted feeding improves insulin sensitivity. Cell Metab 2018
10. American Heart Association. 8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death (conference abstract, March 2024)

Photo: Lisa Lilo