The Medifast diet is a portion-controlled, low-fat, low-carbohydrate, low-calorie diet plan that utilizes meal replacement foods that are obtained from the Medifast company in the United States. These meal replacement foods are nutrient-dense and low-calorie. As a low-calorie diet, the Medifast diet is intended to produce rapid weight loss at the start of a weight-loss program for people who are moderately to extremely obese.


The Medifast diet was created and is marketed by Jason Pharmaceuticals, based in Owings Mills, Maryland. Dr. William Vitale founded the company in 1980. Originally, Medifast was primarily a medically supervised weight-loss program. Medifast still offers this option, but only about 10% of its customers now utilize the diet under mandatory medical supervision. Currently an individual can access the Medifast diet program through Medifast Weight Loss Centers, at home by telephone, or through the website ( ), through hospitals or clinics, or through the office of a healthcare provider (for example, a physician, nutritionist, or dietitian).


Glucose is generally regarded as the preferred energy source for cells in the body, with ketosis being regarded as the crisis reaction of the body to a lack of carbohydrates in the diet. In a diet that does not substantially contribute to blood glucose, the body goes through a set of stages to enter ketosis. After about 48 hours, the body starts using ketones produced from stored fats for energy, releasing free fatty acids, while reserving glucose for important needs, thus avoiding the depletion of the body's stored protein in the muscles. The burning of fat is thought to provide sufficient levels of energy while helping to eliminate physical hunger. Ketosis can be deliberately induced through the use of a low-calorie, low-carbohydrate diet, such as the Medifast diet, resulting in rapid weight loss due to the use of body fat for energy.

Specifically, the Medifast diet is a weight-loss program that relies on meal replacement food products that are purchased from Jason Pharmaceuticals. Although medical supervision of the Medifast diet is not required, it is recommended. Medifast offers more than 50 different meals that a dieter may choose, including shakes, bars, drinks, oatmeal, chili, soups, and puddings. The daily calorie intake on the plan is between 800 to 1,000 calories per day. During the weight-loss phase of the diet, the dieter follows a 5 & 1 meal plan that consists of five portion-controlled, nutritionally balanced Medifast meals plus one Lean & Green meal. The Lean portion of the Lean & Green meal consists of either:


Medifast® product

Calories per serving

Protein (g)

Carbohydrates (g)

Fat (g)

Cholesterol (mg)

Sodium (mg)

Potassium (mg)

Fiber (g)

55 shakes









70 shakes









Ready-to-drink shakes









Appetite suppression shakes









Diabetic shakes









Women's health shakes


















Diabetic bars


















Amounts vary with product flavors

The Green portion of the Lean & Green meal consists of:

A person who chooses to replace all meals with Medifast food products and to not incorporate the Lean & Green meal into their diet must do so only under a doctor's supervision.

During the Medifast 5 & 1 weight loss phase, the dieter eliminates fruits, dairy, and starches because of their high carbohydrate content. These foods can be reintroduced into the diet during the maintenance phase of the Medifast program. The dieter is also directed to drink at least 64 ounces of water per day and to limit the intake of other noncaloric liquids, although additional noncaloric beverages are allowed. Coffee and caffeinated drinks are limited to three per day, as the low caloric level of the Medifast diet may increase sensitivity to caffeine, resulting in anxiety or shakiness. Alcoholic beverages are not recommended on the Medifast program because they provide additional calories without nutritional value. Alcohol also stimulates the appetite as well as depletes the body of water.

The protein used in Medifast meal products is soy protein, a complete protein, which provides all the essential amino acids required for nutrition. The benefits of soy protein include:

Medifast offers different formulations of their shakes: Medifast 55 and Medifast 70 are used, respectively, for men and women. All the low-lactose shakes contain proteins, vitamins, and minerals. Medifast 70 has a higher soy protein content and is more suitable for men or for women who are physically very active. In addition, a Medifast Plus Shake for Appetite Suppression is available that contains an appetite suppressant in addition to protein, vitamins, and minerals. A variety of lactose-free or low-lactose products are available for people who are lactose intolerant.

The dieter is allowed one snack a day on the Medifast diet. These snacks may be Medifast snacks purchased through the program or such items as celery stalks, sugar-free gelatin, sugar-free gum, sugar-free mints, bouillon, sugar-free popsicles, or dill pickle spears. Medifast products are sweetened with fructose or acesulfame potassium. The company's diet products do not contain any stimulants, ephedrine, or herbs. Additional vitamin supplements are not required with the Medifast program because the Medifast meals are fortified with vitamins. Most Medifast meal replacement products contain about 3–4 grams of fiber. Only one Medifast bar is allowed per day on the diet, as the bars are higher in calories than the other Medifast food products. Meals can be seasoned with herbs, seasonings, or spices, but the use of condiments such as ketchup, mustard, soy or teriyaki sauce, vinegar, or horseradish is limited to small amounts of not more than 3–4 condiments a day. To accommodate eating at restaurants while still adhering to the Medifast diet, the dieter can have the daily Lean & Green meal.

For people with various allergies, Medifast provides information on allergens present in specific Medifast food products. These allergens include whey, milk, soy, lactose, wheat, eggs, shellfish, tree nuts, peanuts, caffeine, and gluten.

All Medifast food products meet the standards imposed by the U.S. Food and Drug Administration for standards, labeling, and packaging requirements for the marketing and sale of medical foods, vitamins, and nutritional products. As part of the medical food labeling requirement, each product lists the name and quantity of each ingredient and is identified as a weight management/modified fasting or fasting supplement. The majority of Medifast products are certified kosher by The Orthodox Union of New York. In addition, a number of vegetarian meals and snacks are available. A vegetarian can replace the meat portion of the Lean & Green meal with such items as low-fat cheese, eggs or egg substitute, tofu, cottage cheese, or vegetable burgers.

Several specialized Medifast food products and supplements can be used in conjunction with the Medifast 5 & 1 diet program. Individuals should not incorporate more than one kind of supplement into their Medifast meal plan.

Medifast Plus for Joint Health is a meal-replacement supplement that was formulated to relieve the symptoms associated with arthritis and poor joint health. Medifast Joint Health Shakes contain both glucosamine and chondroitin. Three Joint Health Shakes are included daily as part of the Medifast 5 & 1 Meal plan. Individuals who are already taking medication for arthritis should consult with their healthcare providers before incorporating Joint Health Shakes into their Medifast diet plan.

Medifast Plus for Women's Health is a meal-replacement supplement that was formulated to relieve and prevent the symptoms of menopause, such as hot flashes and night sweats. The Women's Health Shakes contain black cohosh, echinacea, and chaste tree berry. One to three Women's Health Shakes are included daily as part of the Medifast 5 & 1 meal plan. Women who are already on hormone replacement therapy should consult with their healthcare providers before incorporating Women's Health Shakes into their Medifast diet plan.

Medifast Plus for Coronary Health is a meal replacement supplement that was formulated to protect the heart against disease. Coronary Health Shakes include Coenzyme Q10, amino acids, and Pycnogenol. One to three Coronary Health Shakes are included daily as part of the Medifast 5 & 1 meal plan. The Coronary Health Shake was designed as a preventive measure, and people with concerns about their heart health should talk to their healthcare providers before using this Medifast food product. It is especially important that people who are already on heart medications consult with their doctors before incorporating Coronary Health Shakes into their Medifast diet plan. In addition, dosage levels of blood pressure medications may need to be adjusted as a person loses weight.

Exercise is an integral part of losing weight and maintaining weight loss. A person who does not have an exercise program in place prior to starting the Medifast diet should wait two to three weeks before beginning an exercise program to prevent dehydration and to protect muscle tissue. A person who does participate in an exercise program before starting the Medifast diet should cut the exercise program in half for the first several weeks to allow the body to adjust to the lower calorie levels. As the body adjusts, the length and intensity of exercise can be increased.

A person stays on the Medifast 5 & 1 plan until:

If a person has significant weight to lose that necessitates staying on the weight loss phase for longer than 16 weeks, the program should be monitored by a healthcare provider.

During the transition phase, after the weight loss phase of the Medifast diet, calories are slowly added back into the diet to give the body time to adjust to the new levels of calories and carbohydrates. Following the transition phase, an individual should develop a plan to maintain the weight loss. In some cases, a person may choose to continue to include Medifast food products in conjunction with other low-calorie meals to maintain a healthy weight. People experiencing a weight gain of five to ten pounds may go back on the Medifast 5 & 1 plan for a few weeks to return to their target weights.

According to the Medifast website, their diet cost approximately $10 per day in 2018. The 14-day kits ranged in price from $156 to $215, and the 30-day kits averaged from $395 to $460, depending on the number of servings and types of foods selected. Costs are higher when purchasing on a per-product basis. No enrollment or membership fees are associated with the program. The Medifast program has a web-based support program for customers that provides dieters with tools, support, and information to assist with nutrition, exercise, and motivation. The program also provides behavior modification programs. In August 2002, Jason Pharmaceuticals set up a health network subsidiary, Take Shape for Life, that involves physicians and medical professionals to supervise a network of qualified health advisors who work with individuals to help them successfully implement their Medifast diet plan.



Many people on the Medifast diet lose an average of two to five pounds per week. Individual results vary based on initial weight when starting the program, targeted weight-loss goal, level of exercise, presence of medical conditions, use of medications, and compliance with the diet requirements.


Before starting the Medifast diet program, individuals should consult with their healthcare providers. This is especially important for those who:

All individuals taking prescription medications should periodically meet with their healthcare providers while on the Medifast diet to ensure they are taking the correct medication dosages while on the diet. People over the age of 70 must be under the supervision of a healthcare provider when using the Medifast diet because they may need a higher caloric intake and may need to adjust their dosages of medications.

The Medifast meals should be eaten every two to three hours. If a meal is missed, the rest of the meals should be eaten closer together, for if a meal is skipped, the nutrients for the day will be inadequate.

Some difficulties may occur when transitioning from a diet based on shakes and soups to a regular diet. The transition phase should last about four to six weeks and can be started by introducing foods such as oatmeal for breakfast and fruits for snacks. Due to the low caloric intake during the weight loss phase of the Medifast diet, it is likely that some muscle loss will occur, so gradually increasing strength training during the transition phase is recommended.


Certain conditions absolutely prohibit the use of a low-calorie diet such as Medifast. These conditions include:

Other conditions may limit the use of Medifast products and require the close supervision of a healthcare provider. These conditions include:

Acesulfame potassium—
A calorie-free artificial sweetener, also known as Acesulfame K or Ace K, marketed under the trade names Sunett and Sweet One. Acesulfame potassium is 180–200 times sweeter than sucrose (table sugar), as sweet as aspartame, about half as sweet as saccharin, and one-quarter as sweet as sucralose. Like saccharin, it has a slightly bitter aftertaste, especially at high concentrations. Kraft Foods has patented the use of sodium ferulate to mask acesulfame's aftertaste. Alternatively, acesulfame K is often blended with other sweeteners (usually sucralose or aspartame).
Deep vein thrombosis (DVT)—
Blockage of the deep veins; particularly common in the leg.
Premenstrual syndrome (PMS)—
A syndrome that involves symptoms that occur in relation to the menstrual cycle and which interfere with a woman's life. The symptoms usually begin 5 to 11 days before the start of menstruation and usually stop when menstruation begins, or shortly thereafter. Symptoms may include headache; swelling of ankles, feet, and hands; backache; abdominal cramps or heaviness; abdominal pain; bloating or fullness; muscle spasms; breast tenderness; weight gain; recurrent cold sores; acne flare-ups; nausea; constipation or diarrhea; decreased coordination; food cravings; less tolerance for noises and lights; and painful menstruation.
Pulmonary embolism—
Lodging of a blood clot in the lumen (open cavity) of a pulmonary artery, causing a severe dysfunction in respiratory function. Pulmonary emboli often originate in the deep leg veins and travel to the lungs through blood circulation. Symptoms include sudden shortness of breath, chest pain (worse with breathing), and rapid heart and respiratory rates.
Trade name of a commercial mixture of bioflavonoids (catechins, phenolic acid, proanthocyanidins) that exhibits antioxidative activity.
Transient ischemic attack (TIA)—
A neurological event with the signs and symptoms of a stroke, but which go away within a short period of time. Also called a mini-stroke, a TIA is due to a temporary lack of adequate blood and oxygen (ischemia) to the brain. This is often caused by the narrowing (or, less often, ulceration) of the carotid arteries (the major arteries in the neck that supply blood to the brain). TIAs typically last 2 to 30 minutes and can produce problems with vision, dizziness, weakness, or trouble speaking.
Type 1 diabetes—
Previously known as “insulindependent diabetes mellitus,” (IDDM) or “juvenile diabetes.” A life-long condition in which the pancreas stops making insulin. Without insulin, the body is not able to use glucose (blood sugar) for energy. To treat the disease, a person must inject insulin, follow a diet plan, exercise daily, and test blood sugar several times a day. Type 1 diabetes usually begins before the age of three.
Type 2 diabetes—
Previously known as “noninsulindependent diabetes mellitus,” (NIDDM) or “adultonset diabetes.” About 90%–95% of people who have diabetes have type 2 diabetes. People with type 2 diabetes produce insulin, but either do not make enough insulin or their bodies do not use the insulin they make. Most of the people who have this type of diabetes are overweight.

Research and general acceptance

More than 15,000 physicians in the United States have recommended Medifast programs to their patients, and more than a million people have used the Medifast diet since 1980. The Medifast diet is most suitable for people who need to lose a significant amount of weight, and it can be effective, but as with all diets, relapses are common. To maintain the weight loss, the use of a fitness routine is recommended to increase metabolism and lean muscle mass. The Medifast diet can also be expensive, especially when ongoing medical oversight is included.

The Johns Hopkins Weight Management Center in Baltimore, Maryland, uses Medifast food products for their very low-calorie diets. In a clinical study, researchers at Johns Hopkins found that males lost an average of 67.41 pounds and females lost an average of 47.5 pounds after being on the Medifast program for six weeks.


The largest study of Medifast was published in 2015 and conducted by Medifast-affiliated researchers. The retrospective study included 310 overweight and obese clients using the 4&2&1 Plan. The researchers found significant fat mass loss at both 12 and 24 weeks on the plan in men and women of all ages, including those over age 65 years. Data on weight loss at 12 weeks, however, was only reported for 60 participants.

Good evidence of long-term success with the Medifast diet is lacking, as are comparisons with other low-calorie diets. Because it is a very low-calorie and restrictive diet, Medifast may be challenging to combine with regular exercise due to the dieter's lack of energy. Although Medifast may work in the shortterm for rapid weight loss, followers must eventually transition to a maintenance phase; studies detailing longer-term results for those transitioning from the initial Medifast diet are lacking.

See also Calorie restriction ; Low-fat diet ; Metabolism .



Davis, Lisa, Bradley T. MacDonald, and Wayne S. Andersen. The Secret Is Out: Medifast, What Physicians Have Always Known about Weight Loss. Owings Mill, Maryland: Medifast, 2007.


Coleman, Christopher D., Jessica R. Keil, Andrea Hanlon-Mitola, et al. “Effectiveness of a Medifast Meal Replacement Program on Weight, Body Composition and Cardiometabolic Risk Factors in Overweight and Obese Adults: A Multicenter Systematic Retrospective Chart Review Study.” Nutrition Journal 14, no. 1 (August 6, 2015): 77.

Coleman, Christopher D., Jessica R. Keil, Andrea Hanlon-Mitola, et al. “Use of the Medifast Meal Replacement Program for Weight Loss in Overweight and Obese Clients: A Retrospective Chart Review of Three Medifast Weight Control Centers (MWCC).” Food and Nutrition Sciences 3 (2012): 1433–4.


Best Diet Rankings. “Medifast” U.S. News & World Report. (accessed May 29, 2018).

Medifast. “Medifast Official Website.” . (accessed May 28, 2018).


Academy of Nutrition and Dietetics, 120 S. Riverside Plaza, Ste. 2190, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600,, .

American Society for Nutrition, 9211 Corporate Blvd., Ste. 300, Rockville, MD, 20850, (240) 428-3650, Fax: (240) 404-6797, .

American Vegan Society (AVS), 56 Dinshah Lane, PO Box 369, Malaga, NJ, 08328, (856) 694-2887, Fax: (856) 694-2288, .

British Nutrition Foundation, New Derwent House, 69-73 Theobalds Rd., London, UK, WC1X 8TA, +44 20 7557-7930,, .

Center for Food Safety and Applied Nutrition, Food and Drug Administration, 5001 Campus Dr., HFS-009, College Park, MD, 20740-3835, (888) 723-3366, .

Tish Davidson, AM
Revised by Jennifer E. Van Pelt, MA

  This information is not a tool for self-diagnosis or a substitute for professional care.