What Is the Overnight Diet?

Overnight diet

Verywell / Debbie Burkhoff

Losing weight while you sleep sounds like a dream come true. But according to Caroline Apovian, MD, creator of the Overnight Diet, that's exactly what will happen if you follow her plan, which claims you can lose up to nine pounds in a week.

Dr. Apovian is an established physician, professor of medicine, and obesity researcher at Boston University. Her book, "The Overnight Diet: The Proven Plan for Fast, Permanent Weight Loss," is based on her research and experience working with overweight patients.

The Overnight Diet premise is based on the theory that getting a good night's sleep can curb hunger hormones and help you lose weight. In fact, Dr. Apovian says that following her two-part eating plan and getting a full eight hours of sleep each night will put your body into a fat-burning mode so that you can lose "up to two pounds overnight and up to nine pounds the first week, and every week thereafter."

This low-calorie eating plan emphasizes whole foods. It's also very high in protein and restricts processed foods, added sugars, and refined carbohydrates. But the diet also involves a smoothie-only fasting day, which could make it hard for some people to sustain. Also, there is no maintenance phase after the diet—Dr. Apovian says to continue the diet after reaching your goal weight to maintain it.

Some people might find it difficult and time-consuming to plan and prepare whole-food meals (no convenience foods are allowed), consume only smoothies one day a week, and fit in all the sleep and exercise required on the Overnight Diet. While components of this plan are certainly healthy, it is generally not recommended by nutritionists. There are more balanced approaches to weight loss.

What Experts Say

"The Overnight Diet is a low-carbohydrate, calorie-restrictive weight loss plan that includes smoothie fasts and sleep guidelines. Experts agree sleep is vital for health, but restrictive diets are not sustainable, can lead to weight gain, and can cause nutrient deficiencies."

Willow Jarosh, MS, RD

What Can You Eat?

With an emphasis on whole foods, the Overnight Diet eliminates refined carbohydrates and processed foods. The eating plan allows unlimited fruits and non-starchy vegetables on "Fuel Up" days, which are also included in "Power Up" smoothie days.

High in protein, the Overnight Diet claims to help people build and retain muscle as they lose fat. Dr. Apovian says that protein is important because it builds muscle mass. "We have realized that as you get older, you need more protein, not less—the body loses one percent muscle mass per year after the age of 30," she said in a 2013 interview with BU Today. As you lose muscle, your metabolic rate decreases, and you cannot eat as much as you used to—therefore, you gain weight. Eating protein prevents this "shrinking muscle syndrome" and also helps you feel full.

There is a bit of math involved in calculating your daily protein requirement and planning protein-rich meals to meet that requirement. However, there is no calorie counting on this plan. Other than the one-day off, six-days on method, Dr. Apovian doesn't provide any guidance on the number or timing of meals and snacks.

What You Need to Know

It's important to note that the Overnight Diet is much more than just getting enough sleep. It's about changing what and how you eat. First, you restrict calories by fasting one day each week. On this "Power Up" day, you avoid solid food and only drink smoothies (made with fruits, vegetables, nonfat milk or milk substitutes, and protein from yogurt or protein powder). On the remaining six "Fuel Up" days, you stick to a diet of lean protein, fruits, and vegetables. You don't count calories, measure points, or restrict portion sizes.

Dr. Apovian's book includes recipes, a meal plan, a guide to eating out, and an exercise plan for a 21-minute workout to be done four times a week. And, of course, the author recommends getting a good night's sleep. Studies have shown that our bodies release a hunger hormone called ghrelin when we don't get enough sleep. When that happens, your body starts to behave as if it needs more food. You get hungry, your stomach starts to grumble, and you may even conserve fat to avoid starvation.

Feeling energized and well-rested may help to curb hunger hormones and promote daily movement to burn more calories. Some studies have shown an association between improved sleep hygiene and weight loss, but more research is still needed to determine the exact role of sleep.

As with any high-protein diet, consult your doctor before trying this eating plan if you have kidney disease. You should also use caution with the once-weekly "Power Up" (smoothie) day if you have diabetes. Be sure to check with your doctor before trying this weight loss method.

What to Eat
  • Lean protein

  • Fruits

  • Vegetables

  • Whole grains

What Not to Eat
  • Processed foods

  • Added sugars and sweeteners

  • Refined carbohydrates

Lean Protein

Dr. Apovian advocates eating double the recommended daily allowance of protein and consuming plenty of protein every day (not skipping any days). There is a formula in the book for calculating your daily protein requirement.

Whole Grains

While this is a low-carb plan, whole grains are permitted. Dr. Apovian calls whole grains, fruits, and non-starchy vegetables "lean carbs."

Refined Carbohydrates

Because carbs are not as satiating as protein, you need to eat more of them to feel full. That, in turn, leads to more calorie consumption, which contributes to weight gain. Therefore, refined carbohydrates like white bread, rice, and pasta are not permitted on this eating plan.

In Dr. Apovian's view, you're not necessarily giving up these foods because she does not consider processed and high-sugar foods as real food.

Pros and Cons

  • Encompasses lifestyle changes

  • Emphasizes whole foods

  • Little counting or measuring

  • Restrictive

  • Overpromises on weight loss

You won't have to count calories, carbs, or serving sizes on this plan. The only thing you will need to know is your daily protein requirement and then plan your meals to meet it. This weight loss program may work for some people, but not without some hard work. Losing weight is about more than just getting a good night's sleep, even though the name of this diet may suggest otherwise.

Although Dr. Apovian says there's no deprivation on the Overnight Diet, the plan cuts out processed foods, which are a large part of the standard American diet, due to their affordability and convenience. It also limits carbohydrates and calls for no solid foods at all for one day per week. Not everyone may find this eating plan feasible due to factors like budget and time constraints.

But whole foods are typically healthier than processed foods; they offer nutrients and fiber without added sugar, salt, or fat. If you currently eat a standard diet that includes more starchy carbohydrates, fat, and sugar, switching to this strict eating style will probably result in a calorie deficit.

If you follow this plan perfectly, you're likely to cut enough calories to lose a few pounds per week. And Dr. Apovian is careful to say that the Power Up days can promote a loss of up to two pounds, for up to nine total pounds lost per week. In reality, however, this is not a realistic amount of weight to lose for most people in the short term. Additionally, the restrictive eating plan may be difficult for some people to stick to for the long term.

If your expectation is to lose nine pounds per week, you may get frustrated and quit if that doesn't happen. A healthy, balanced diet does not typically produce this amount of fat loss that quickly.

Is the Overnight Diet a Healthy Choice for You?

The USDA 2020–2025 Dietary Guidelines for Americans recommends consuming various nutrient-dense foods such as fruits and vegetables, legumes, whole grains, lean protein, low-fat dairy products, and healthy fats. The USDA also recommends limiting foods and beverages with higher amounts of added sugars, saturated fat, and sodium and also limiting the consumption of alcoholic beverages.

The Overnight Diet advises eating about double the amount of protein suggested in federal dietary guidelines. That crowds out some other foods, notably carbohydrates, which are still recommended by the USDA as part of a healthy, balanced diet. The USDA doesn't advocate "smoothie days" either.

Dr. Apovian says calorie counting isn't necessary. But for many people, determining a calorie target (one that creates a calorie deficit) and adhering to it is a good weight-loss strategy. For weight maintenance, the USDA recommends a daily calorie intake of about 1,600 to 2,400 calories per day for women and 2,000 to 3,000 calories per day for men, but that number varies greatly depending on weight, age, sex, and activity level. To lose weight, you will need to reduce calories below what you are consuming through diet. Use this tool to calculate your daily calorie needs to meet your weight loss goal.

The Overnight Diet is based on established weight-loss strategies and shares some similarities with other effective weight-loss programs, such as cutting calories, added sugars, and refined carbs, and promoting intermittent fasting. However, it is too restrictive to meet some expert guidelines on nutrition.

Health Benefits

Despite its restrictive eating plan, "The Overnight Diet" book does include recommendations for sleep and exercise. However, there is little advice in the book on improving sleep quality and duration, and the suggested exercise routine might not work for everyone. Regardless, getting enough sleep and exercise is important. Research continues to show an association between improved sleep and an increased willingness to exercise, which can lead to weight loss.

Health Risks

While there are no common risks associated with the Overnight Diet, it overpromises rapid weight loss results of nine pounds in a week. Experts generally agree that a reasonable rate of weight loss is 1–2 pounds per week. Research shows that weight loss resulting from restrictive dieting is not always sustainable and can lead to weight regain.

Additionally, the Overnight Diet restricts healthy food groups on smoothie-only days, which is not advisable for the long term and could lead to nutrient deficiencies. A more sustainable approach would include a variety of nutrient-dense foods in your diet each day.

A Word From Verywell

Getting a good night's sleep, exercising regularly, and eating a nutritious diet with plenty of lean protein, fruits, and vegetables is a smart weight-loss plan. But you don't necessarily have to buy a book and subscribe to a restrictive eating program to make those changes in your life. Keep in mind that while Dr. Apovian is a knowledgeable physician, she's not your physician. So her advice isn't customized to your specific needs. If you're looking to lose weight, talk to your own doctor about the best ways to do so.

Remember, following a long-term or short-term diet may not be necessary for you, and many diets out there don’t work, especially long-term. While we do not endorse fad diet trends or unsustainable weight loss methods, we present the facts so you can make an informed decision that works best for your nutritional needs, genetic blueprint, budget, and goals.

If your goal is weight loss, remember that losing weight isn’t necessarily the same as being your healthiest self, and there are many other ways to pursue health. Exercise, sleep, and other lifestyle factors also play a major role in your overall health. The best diet is always the one that is balanced and fits your lifestyle.

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5 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Broussard JL, Kilkus JM, Delebecque F, et al. Elevated ghrelin predicts food intake during experimental sleep restrictionObesity (Silver Spring). 2016;24(1):132-138. doi:10.1002/oby.21321

  3. Chaput J-P, Tremblay A. Adequate sleep to improve the treatment of obesityCMAJ. 2012;184(18):1975-1976. doi:10.1503/cmaj.120876

  4. U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2020–2025 Dietary Guidelines for Americans. Ninth Edition. December 2020.

  5. Dolezal BA, Neufeld EV, Boland DM, Martin JL, Cooper CB. Interrelationship between sleep and exercise: a systematic reviewAdv Prev Med. 2017;2017:1364387. doi:10.1155/2017/1364387

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