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Research and general acceptance



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. 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 persons 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


Calories per
55 shakes901113—140—10250 420—4403
70 shakes100—1101413—140.5—10240—250400—4303
Appetite suppression
Diabetic shakes90149—100.5—102504003
Women’s health
Diabetic bars14010—1123—234—5.50160—170320—3504

Amounts vary with product flavors

(Illustration by GGS Information Services/Thomson Gale.)

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 the Medifast diet program through Hi-Energy Weight Loss Centers, at home by telephone or through the web site (, through hospitals or clinics, or through the office of a health care provider (for example, a physician, nutritionist, or dietitian). Medifast is available in Asia (India, Hong Kong, and Singapore) as Dr. Diet.


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. There are over 50 different meals that a dieter may choose as part of the diet, 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:

  • five ounces of cooked lean beef, pork, or lamb
  • seven ounces of cooked chicken, turkey, fish, or seafood.

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

  • Two cups of salad greens with 1/2 cup of raw vegetables (cabbage, spinach, sprouts, celery, radishes, cucumber, pepper, or tomato and 1-2 tablespoons of low-carb salad dressing, or
  • One and one-half cups of low-carbohydrate cooked vegetables (Carrots, corn, peas, potatoes, and Brussels sprouts should be avoided during the weight loss phase of the Medifast diet).

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 non-caloric liquids,


Acesulfame potassium — A calorie-free artificial sweetener, also known as Acesulfame K or Ace K, and 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 the sweetness of 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)

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

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 the 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

Pycnogenol— Trade name of a commercial mixture of bioflavonoids (catechins, phenolic acid, proan, thocyanidins) that exhibits antioxidative activity

Type 1 Diabetes— Previously known as insulin-dependent diabetes mellitus, (IDDM) or juvenile diabetes. Type 1 diabetes is 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 3.

Type 2 Diabetes— Previously known as noninsulin-dependent diabetes mellitus(NIDDM) or adult-onset diabetes. Type 2 diabetes is the most common form of diabetes mellitus. About 90 to 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

although additional non-caloric 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, as 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, which as a complete protein, provides all of the essential amino acids required for nutrition. The benefits of soy protein include:

  • potential lowering of blood cholesterol levels, especially levels of LDL cholesterol
  • potential increase in the mineral content and density of bones, which may protect against bone fractures and osteoporosis
  • possible prevention of hormone-related cancers such as breast cancer, prostate cancer, and colon cancer
  • possible reduction in triglycerides and increase in HDL cholesterol
  • possible reduction in menopausal symptoms, including hot flashes or night sweats

Different formulations of the Medifast shakes, Medifast 55 and Medifast 70, are used for men and women. All of the low-lactose shakes contain proteins, vitamins , and minerals. However, Medifast 70 has a higher soy protein content and is more suitable for men or for women who are physically very active. In addition, there is a Medifast Plus Shake for Appetite Suppression available that contains an appetite suppresant in addition to protein, vitamins, and minerals. There are also a variety of lactose-free or low-lactose products available for persons 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-ree gum, sugar-free mints, bouillon, sugar-free popsicles, or dill pickle spears. Medifast products are sweetened with fructose or acesulfame potassium. Medifast diet products do not contain any stimulants, ephedrine, or herbs. Additional vitamin supplements are not required with the Medifast program, as the Medifast meals are fortified with vitamins. There are about 3-4 grams of fiber in most Medifast meal replacement products. 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, 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 persons 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 United States 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, there are a number of vegetarian meals and snacks 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.

There are several specialized Medifast food products and supplements that can be used in conjunction with the Medifast 5 & 1 diet program. However, individuals should not incorporate more than one kind of supplement into their Medifast meal plan.

Medifast Plus for Diabetics is designed to meet the nutritional needs of persons with Type 2 diabetes. This Medifast program can be used as a supplement in a weight-loss program for a person with Type 2 diabetes or as a supplement to a diabetes diet that has been designed to control blood sugar. The Medifast food products for diabetics contain less than 5 grams of sugar per serving, and many of the products have been certified as Low Glycemic by the Glycemic Research Institute. Blood sugar, oral diabetes medications, and insulin needs must be monitored periodically and adjusted as needed. Blood sugar should be checked at least two to three times a day, especially at the beginning of the Medifast program.

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. A person who is already taking medication for arthritis should consult with their health care provider 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. A women who is already on Hormone Replacement Therapy should consult with their health care provider before incorporating Joint 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 persons with concerns about their heart health should talk to their health care provider before using this Medifast food product. It is especially important that persons who are already on heart medications consult with their health care provider 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. However, a person who does not have an exercise program in place prior to starting the Medifast diet should wait 2-3 weeks before beginning an exercise program, in order 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:

  • the target weight has been met
  • weight loss has slowed to less than three pounds per month
  • the dieter develops a contraindication to the program, such as pregnancy
  • the health care provider recommends transitioning into the maintenance phase

If a person has significant weight to lose that necessitates staying on the weight loss phase for longer than sixteen weeks, the program should be monitored by a health care 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 choses to continue to include Medifast food products in conjunction with other low calorie meals to maintain a healthy weight. Persons experiencing a a weight gain of five to ten pounds may go back on the Medifast 5 & 1 plan for a few weeks in order to return to their target weight.

As of 2007, the Medifast diet costs about $10/day, $70/week, or $275/month when purchasing food in packages. Costs are higher when purchasing on a per-product basis. There are no enrollment or membership fees associated with the program. The Medifast program has a web-based support program for customers that provides the dieter with tools, support, and information to assist with nutrition, exercise, and motivation. The program provides also behavior modification programs. In August 2002 Jason Pharmaceuticals set up a health network subsidiary, Take Shape for Life, that by 2007 had enrolled over 150 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.


The purpose of the Medifast diet is create a calorie deficit that allows a person to burn fat and lose weight while maintaining muscle mass. The Medifast diet is most suited for those persons who need to lose a significant amount of weight and have had difficulty losing weight with other diets.


Many people on the Medifast diet lose an average of 2-5 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, a person should consult with a health care provider. This is especially important if the person:

  • has any serious medical conditions
  • is on any medications, especially those for diabetes
  • is age 65 or older
  • is under the age of 18
  • has 50 pounds or more to lose.

All individuals taking prescription medications should periodically meet with their health care provider while on the Medifast diet to make sure that medication dosages while on the diet. Persons over the age of 70 must be under the supervision of a health care provider when using the Medifast diet. These older people 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.

There may be difficulties associated with 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 level of 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:

  • Mycocardial infarction/heart attack within previous three months, unstable angina
  • Strokes or transient ischemic attacks
  • Uncontrolled seizures
  • Clotting disorders
  • Type 1 diabetes (unless Medifast food products are used to improve nutrition or weight maintenance, but Medifast is not recommended as a weight loss program for Type 1 diabetics
  • Severe liver or kidney diseases that require low-protein diets
  • Active peptic ulcer disease
  • Active cancers
  • Active thrombophlebitis (or Deep Vein Thrombosis (DVT)/Pulmonary Embolism (PE) within three months
  • Pregnancy or breast-feeding
  • Eating disorders such as anorexia or bulimia
  • Severe psychiatric illnesses, including history of major depression and/or suicide attempts
  • Corticosteroid therapy of greater than 20 mg per day
  • Chronic illicit drug use, addictions, alcoholism, and/ or substance abuse.

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

  • Use of the medication Lithium (blood lithium levels should be monitored during the use of the Medifast diet)
  • A history of seizures
  • A history of peptic ulcer disease
  • Use of anticoagulant medications such as coumadin (blood tests should be performed to determine the therapeutic level of coumadin required during the use of the Medifast diet)
  • Over the age of 70 (it is recommended that persons use Medifast products in conjunction with a 1,200 calorie per day diet)
  • Adolescent use (after puberty and under the age of 18, the Medifast diet should only be used under the care of a health care provider
  • Hypothyroidism (the Medifast diet should only be used under the direct supervision of the health care provider. Blood tests should be conducted throughout the period of the diet and medication adjusted as required. Some health care providers suggest that a non-soy Medifast product be eaten at the time of day that the thyroid medication is taken.
  • Gastric by-pass surgery (the Medifast diet can be used in conjunction with gastric bypass surgery but calorie levels may be adjusted at the recommendation of the health care provider.

Many people do not experience physical discomfort on the Medifast program. However, some persons may become constipated, feel dizzy, lightheaded, fatigued, and/or cold, and may develop dry skin and hair. Other effects may include leg cramps, headaches, hair loss, rashes, gas, diarrhea, bad breath, and excessive feelings of hunger. For women, the rapid weight loss associated with the Medifast diet may cause an increase in levels of estrogen in the blood stream, which can affect the regularity of menstrual cycles, possibly increase symptoms of premenstrual syndrome (PMS), and can also increase fertility.

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 persons have used the Medifast diet since 1980. The Medifast diet is most suitable for persons who need to lose a significant amount of weight. The Medifast diet 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 on-going 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.

In an 86-week weight loss study of persons with Type 2 diabetes, which was funded by Medifast, researchers from Johns Hopkins Bloomberg School of Public Health found that participants using Medifast lost twice as much weight and were twice as compliant as participants following a standard food diet based on the dietary guidelines of the American Diabetes Association (ADA). Twenty-four percent of the Medifast dieters were able to decrease or eliminate


  • Is this type of low calorie diet appropriate for my weight-loss needs?
  • What types of medical monitoring and oversight do I need?
  • Where can I find support and information?
  • What types of side effects should I watch out for?

their diabetes medication, compared to zero percent on the standard ADA food diet.

As of 2007, the National Institutes of Health is sponsoring a study on energy metabolism in the post-obese state at The University of Vermont. Medifast products are being used as the weight loss tool in the study. The study found that after 8 months, participants lost 45–65 pounds. Other users of the Medifast diet include the Shands Teaching Hospital, which is affiliated with the University of Florida, as part of their adolescent obesity treatment program and the Maine State Prison in their weight-loss program for obese prisoners.



Davis, Lisa, and MacDonald, Bradley, T. The Secret is Out: Medifast, What Physicians Have Always Known About Weight Loss. Owings Mill, Maryland: Medifast, Inc., 2006.


Medifast, Inc. Telephone: 800-209-0878. Website: []

Tish Davidson, A.M.

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