Difference Between Optifast & Medifast

In most cases, you should lose weight slowly to ensure you lose fat and not muscle. But in extreme cases, quick weight loss may be necessary to improve serious health conditions such as obesity, diabetes and high blood pressure. Both Optifast and Medifast are low-calorie diets that help you lose weight quickly with meal replacement supplements. While both programs have the same goal, their plans to help you lose the weight are different.

Program Basics

Both Optifast and Medifast plans are divided into three phases: a weight-loss phase, a transition phase and a maintenance phase. On the Optifast plan, the weight-loss phase of the program lasts 12 weeks and the transition phase six weeks, while the maintenance phase is ongoing. Medifast does not set a specific number of weeks for the weight-loss phase of the program. But like Optifast, the transition phase is a set six weeks and the maintenance plan is ongoing.

The Meals

Difference Between Optifast & Medifast

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During the weight-loss phase of the program, both Optifast and Medifast use meal replacement foods to help you reduce caloric intake to 450 to 800 calories a day. However, on the Optifast plan you are only allowed to consume the Optifast products, which include shakes, soups and bars. On Medifast, you consume five meal replacement products, which include shakes, soups, stews, chili, oatmeal, bars, pudding, pretzels and cheese puffs, and one meal consisting of a 5- to 7-ounce portion of a lean meat and a 1 1/2- to 3-cup serving of a nonstarchy vegetable each day.


Optifast is a clinic-based weight-loss program. On the plan, a physician monitors your health, and you receive nutrition support from a dietitian and weekly lifestyle training from a behaviorist. Medifast offers both clinic and web support. At the clinic, your body composition is assessed and monitored. After you've lost the weight, you receive information and encouragement from a trained Medifast weight-control counselor. Medifast also offers 24-hour web support with an online community and phone support with Medifast nutritionists and customer care.

Weight Loss

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According to the Optifast website, weight loss varies, but most people lose more than 50 pounds in 18 to 24 weeks. On the Medifast plan, you are expected to lose 2 to 5 pounds during the first two weeks of the program, and then 1 to 2 pounds each week thereafter.

Helping You Keep the Weight Off

Weight regain is very common following a very low-calorie diet, according to the Weight-control Information Network, making the maintenance portion of these two programs very important. After you lose the weight on Optifast, you are taught how to reintroduce regular food into your diet while continuing to use the meal replacement products to help with weight maintenance. You also continue to receive ongoing support. On Medifast, once you've hit your weight-loss goal, the counselors determine your maintenance calorie needs and help you balance your daily caloric intake with three real-food meals and three Medifast meal replacement products each day.