What Is the Overnight Diet?

Overnight diet

Verywell / Debbie Burkhoff

Overnight Diet (review)
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Is it really possible to lose weight overnight? If it is, it's a dream come true. Who wouldn't want to go to bed and wake up two pounds thinner? According to Caroline Apovian, MD, author of "The Overnight Diet," that's exactly what will happen if you buy her book and follow her plan. In fact, she says that you can lose up to nine pounds per week with her advice.

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


Dr. Apovian is a physician, professor of medicine, and obesity researcher based at Boston University. Her book, "The Overnight Diet: The Proven Plan for Fast, Permanent Weight Loss," was first published in 2013. It is based on Dr. Apovian's research and experience working with overweight patients.

How It Works

According to "The Overnight Diet," 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." 

But note that the weight loss plan isn't really just about sleeping more. 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.

Compliant Foods
  • Lean protein

  • Fruits

  • Vegetables

  • Whole grains

Non-Compliant Foods
  • Processed foods

  • Added sugars and sweeteners

  • Refined carbohydrates

Lean Protein

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 an 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 it also helps you feel full. She advocates eating double the recommended daily allowance of protein and being sure to consume plenty of protein every day (not skipping any days). There is a formula in the book for calculating your daily protein requirement.

Fruits and Vegetables

As with proteins, the Overnight Diet allows unlimited fruits and non-starchy vegetables on Fuel Up days, and they are ingredients in the Power Up day smoothies as well.

Whole Grains

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

Processed Foods, Sugars and Sweeteners

Although the diet claims that there are no foods to give up, that's not quite true. The diet does eliminate processed foods. Dr. Apovian says that you're not giving up foods, because "I do not consider processed foods and high-sugar processed items food," she told "BU Today."

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.

Recommended Timing

Other than the one-day off, six-days on method, Dr. Apovian doesn't provide guidance on the number or timing of meals and snacks.

Resources and Tips

The 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. However, researchers have not yet confirmed that sleep alone can improve or speed up the weight loss process.


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; check with your doctor before trying this method.

Pros and Cons

  • Encompasses lifestyle changes

  • Emphasizes whole foods

  • Little counting or measuring

  • Restrictive

  • Over-promises on weight loss


Lifestyle Changes

The Overnight Diet book includes not just an eating plan, but also recommendations for sleep and exercise. There is little advice in the book on improving sleep quality and duration, and the workout might not work for everyone. But the general idea that sleep and exercise both play a role in weight loss is important.

Whole Foods

Whole foods are usually healthier than processed ones; they offer nutrients and fiber without added sugar, salt, or fat. And on this diet, whole foods are the rule. 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. And the foods you eat may be more healthy than the high-sugar, higher fat foods you currently consume.

Little Counting

You won't have to count calories, carbs, or serving sizes on this diet. 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 implies otherwise. And there are some other downsides as well.



Although Dr. Apovian says there's no deprivation on the Overnight Diet, that is a reach. This plan cuts out processed foods, which are a big part of many people's typical diet, and it also limits carbohydrates. Plus, it calls for no solid food at all for one day per week.

Weight Loss Promises Are Exaggerated

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.

But the plan may be too hard for many dieters to stick to over the long term. And if your expectation is to lose nine pounds per week, you may get frustrated and quit if that doesn't happen. No healthy diet is likely to produce that amount of fat loss, especially for a long period of time. Experts generally agree that a reasonable rate of weight loss is one to two pounds per week.

How It Compares

The Overnight Diet is based on established weight-loss strategies and thus shares some similarities with other weight-loss programs: Cutting calories, added sugars, and refined carbs, for example, as well as intermittent fasting. However, it is too restrictive to meet some expert guidelines on nutrition.

USDA Recommendations

Food Groups

The Overnight Diet advises eating about double the amount of protein suggested in U.S. 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. The USDA recommends a daily calorie intake of about 1600 to 2000 calories for weight loss. Since this varies a lot depending on weight, age, sex, and activity level, use this tool to calculate your calorie goal.

Similar Diets

Dr. Apovian says that her plan is based on two proven methods: Intermittent fasting and a special high-protein diet developed for hospital patients. Here's how the Overnight Diet compares to those types of plans.

Overnight Diet

  • General nutrition: High in protein and whole foods, this diet restricts carbohydrates and processed foods. It aims to help followers build and retain muscle as they lose fat.
  • Practicality: There is some math involved in calculating a daily protein requirement and then planning protein-rich meals to meet that requirement. However, there is no calorie counting. Some followers might find it time-consuming and difficult to plan and prepare whole-food meals (no convenience foods are allowed), to consume only smoothies one day a week, and to fit in all the sleep and exercise that is required.
  • Sustainability: Given the practical considerations and the restrictiveness of the diet, it could be hard for some followers to sustain. And there is no maintenance phase of the diet. Dr. Apovian says to continue the diet after reaching goal weight in order to maintain it.

Intermittent Fasting

  • General nutrition: Intermittent fasting refers to any plan in which users restrict calories significantly on one or two days a week (such as the smoothie days on the Overnight Diet), and eat a normal diet on other days. So whether it is nutritionally balanced depends on what's being consumed on the non-fast days. But cutting back on calories intermittently is generally believed to be safe for most people.
  • Practicality: It certainly requires discipline to consume a quarter of daily calories, as you do on fast days. But otherwise, there are few rules and restrictions on this plan, which makes it appealing for many people.
  • Sustainability: Because it isn't overly restrictive or complicated (like the Overnight Diet can be), and seems to work for weight loss, many users are able to adhere to this diet for long periods of time. However, it is not appropriate for children, teens, women who are pregnant or breastfeeding, and people with a history of disordered eating. It also may not be right for people with diabetes or heart disease.

Protein Power Diet

  • General nutrition: The Protein Power Diet is another high-protein, low-carb plan developed by a pair of medical doctors. It emphasizes protein and also allows fats, but restricts grains and sugar. Unlike the Overnight Diet, it is a phased program that cuts carbs more sharply at first, then reintroduces them.
  • Practicality: This diet has more rules than the Overnight Diet, and requires counting grams or servings of both protein and carbs.
  • Sustainability: Using the phased plan may help some followers adhere to this diet for the long term. It still requires cutting back on carbs for the duration (which can also mean missing out on some nutrients).

Smoothie Diet

  • General nutrition: The premise of the Smoothie Diet (as developed by author Drew Sgoutas) is to replace two meals a day with a smoothie; the third meal of the day should be nutritionally balanced and not too high in calories. The result is a diet that's rich in fruits and vegetables, which is a plus. But it's also low in two essentials, protein and fat, and high in sugar, which sets it apart from the Overnight Diet.
  • Practicality: Sometimes preparing a smoothie is just as much work (shopping, chopping, and cleaning up) as a full meal, and it's hard to manage if you are not at home.
  • Sustainability: Many people tire of a semi-liquid diet, and this one is missing out on some key nutrients. It's meant to last only 21 days, but Sgoutas also recommends repeating the diet regularly. This is a sign that it's not particularly effective, either at initial weight loss or maintaining that loss.

A Word From Verywell

Getting a good night's sleep, exercising regularly, and eating a diet full of healthy lean protein, fruits, and vegetables is a smart plan. But you don't have to buy a book (or special protein shake powder, which Dr. Apovian also markets) to make those changes in your life. Nor do you have to cut back so strictly on carbs. Dr. Apovian is a physician, but 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.

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