Medifast Diet
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Medifast Diet


The Medifast diet consists of eating mainly prepackaged Medifast meal replacements until you reach your desired weight loss. For $290 you get a month’s worth of meal replacements, to be consumed five times per day. Medifast claims that dieters can lose up to 20 pounds per month on their plan.

How Is This Diet Supposed to Work?

The premise of this diet is that by following a very low-calorie diet the body will go into a state of mild ketosis. Ketosis occurs when the body does not have enough calories to use for fuel and turns to stored body fat and muscle to meet energy needs. According to Medifast, their meals contain a “proven combination of carbohydrates and protein” that helps the body to break down fat—not muscle—for fuel.

What’s Involved?

The Medifast diet is divided into three phases: 5 & 1 plan, transition, and maintenance.

The core part of the diet is the 5 & 1 plan, which you follow until you reach your desired weight loss. During this time you get to eat six times per day: five Medifast prepackaged meal replacements and one “lean and green” meal. Medifast provides over 60 meal replacements to choose from, such as soups, shakes, and bars.

All of these products are fortified with vitamins and minerals to help you meet your nutrient needs, which would otherwise be difficult to do since this diet only provides around 800-1,000 calories per day. You provide the daily “lean and green” meal, which consists of 5-7 ounces of lean meat, fish, or poultry, plus 1-2 cups of vegetables or salad. Meals are supposed to be consumed every 2-3 hours so you won't feel too hungry.

After you reach your desired weight loss, you begin the transition phase, which gradually reintroduces you to “regular” food and increases your calorie intake. The final phase of this diet is maintenance, during which you eat mostly regular foods and work continuously to balance the calories you eat with those that you expend. This is done so that you maintain your current weight.

This diet plan offers programs for women, men, and people with diabetes. You can sign up by phone or online, and the meals will be delivered to your home on a monthly basis. The cost is about $150 for two weeks or $290 per month, but it costs a bit more if you want to choose your own meals.

The Medifast plan recommends that its subscribers also engage in regular exercise. Specifically, they recommend low to moderate exercise, such as walking, swimming, or biking starting at 10 minutes per day for three days a week and increasing as tolerated.

Additional Features of This Diet:

  • Free online meal planner, weight-loss tracker, and support
  • Texas and Florida also have weight loss centers where, for an additional fee, you can receive in-person, customized support.

What Does the Research Say?

This diet basically advocates limiting calories so much that the body goes into a mild starvation mode. Research shows that after a period of starvation, people make up for this by eating extra calories once they can eat normally again. This leads to a rapid return of weight. While the gradual transition phase that Medifast advocates may help prevent this “rebound” weight gain, there is currently no research that examines the effectiveness of this approach.

Additionally, there are no reliable scientific studies to back the claim that the Medifast diet is “clinically” proven to promote fat loss, not muscle loss.

Finally, there is no research to support the idea that certain healthful foods—such as whole grains, low-fat dairy products, and fresh fruit, should be avoided to help promote weight loss. These foods are an important source of nutrients, and fruits and whole grains are naturally high in fiber.

There is some research suggesting that meal replacement diets, such as Medifast, may be helpful for people with diabetes who need to lose weight. A recent study conducted at John Hopkins University found that a diet consisting of portion-controlled meal replacements helped obese people with diabetes lose weight and maintain that loss for one year.

Are There Any Concerns With This Diet?

This is a very low-calorie diet. Therefore, talk to your doctor before starting this diet. Because it is so low in calories, it should not be followed by certain groups of people, including women who are pregnant or nursing, very active individuals, and the elderly. Medifast warns of potential side effects, such as constipation, dizziness or lightheadedness, fatigue, feeling cold, and dry skin or hair.

While this diet plan makes an effort to educate clients on how to transition back to a regular diet and then maintain weight loss, it is not the focus of the diet. Ideally, a diet should focus on establishing new, healthful eating behaviors from the onset—not once weight loss is achieved through a “quick fix” plan.

Bottom Line

The Medifast diet is not recommended for most people because it is so low in calories. In addition, eating a diet that consists mostly of meal replacement bars and shakes—versus real food—is unsatisfying and unrealistic for any length of time. The best diets are those that take a healthful approach to eating and can be sustained in the long-term. Rather than investing in this diet, consider meeting with a registered dietitian to come up with a personalized eating plan that you can stick to.


American Dietetic Association

Choosing a Successful Weight-loss Program
Weight-control Information Network


Canada's Food Guide

Dietitians of Canada


Cheskin LJ, Mitchell AM, Jhaveri AD, et al. Efficacy of meal replacements versus a standard food-based diet for weight loss in type 2 diabetes: a controlled clinical trial. Diabetes Educ. 2008;34:118-27.

Human pattern of food intake and fuel-partitioning during weight recovery after starvation: a theory of autoregulation of body composition. Proc Nutr Soc . 1997;56:25-40.

Medifast website. Available at: . Accessed April 30, 2008.

Last reviewed May 2008 by Maria Adams, MS, MPH, RD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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