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Medifast is a publicly traded company listed on the New York Stock Exchange (cost 9/15/17 5 pm EDT per share is $56.48) worth $285 million, give or take. Forbes magazine named it a fastest growing company on its 30th anniversary in 2010 and on its list of “America’s 100 Best Small Companies.”   
In announcing its ranking on Forbes’ lists, Medifast described itself as “a leading portion-controlled weight-loss program.” Actually, Medifast is a very low calorie diet (VLCD) consisting of Medifast prepackaged meal replacement shakes and other foods. It’s also a multi-level-marketing (MLM) diet business, which the company calls its “Take Shape for Life” personal coaching division. Medifast also sells its program and products online and through call centers, in its Medifast Weight Control Centers and through a network of doctors.   
Medifast will sell to anyone online or through distributors, but in its centers people should be at least 30 pounds overweight based on body mass index guidelines. It’s a very big and lucrative business—especially for those at the top of the MLM pyramid.
In 1980, founder/physician William Vitale formulated a severely calorie-restricted diet using prepared meal-replacement foods and shared/sold his program to other doctors. That was the beginning of the more than quarter-billion dollar business today. Think about that; worth $285 million. Wow.
“Medifast is safe and effective to do on your own whether you want to lose 15 or 120 or more pounds.” That’s the weight loss claim. Medifast says it is safe and effective and used by doctors for years. In fact, Vitale sold the diet to fellow doctors and that’s how he got that direct marketing business model rolling. Medifast says tens of thousands of doctors have recommended it over the decades but adds, “It’s only been within the past decade that Medifast was formulated to be available to you without a doctor’s supervision.” 
Medifast weight loss meals are “nutrient-dense and fortified with 24 vitamins and minerals, so you can lose pounds and inches without losing out on nutrition. Each meal has essentially the same nutritional profile, and has been designed to have enough low-fat protein and healthy fiber to help you feel full and satisfied, without the between-meal hunger that can sabotage a weight loss plan.” Medifast says the key to weight loss on its plans is simple: “After a few days on either Medifast weight loss plan, your body will start to burn fat so you can lose weight while preserving muscle tissue.” 
There are two plans. Medifast Go was formerly known as the Medifast 5 & 1 Plan. Let me digress here for a minute; the Medifast 5 & 1 Plan was the subject of a sweeping 2012 federal investigation and lawsuit, wherein federal agencies alleged the company engaged in false advertising when it claimed you’d “lose 2-5 pounds” per week with no scientific proof of that claim. Medifast ultimately settled by paying a $3.7 million fine, but declined to admit guilt. 
Still, going forward it was ordered to provide at least one clinical trial as proof of its claims. (Which is the least it could do, in my opinion; false advertising rips off the public and those desperate to lose weight.) In any event, Medifast now claims it has scientific proof and points to two clinical studies—much more about those shortly—and changed the program name to Medifast Go, and added a new weight loss meal replacement program, Medifast Flex, previously known as the Medifast Achieve Plan. Each will run you around $75 to $100 a week, by the way.
On the Medifast diet you eat “Medifast Meals fortified with the essential vitamins and minerals you need for healthy weight loss.” Medifast claims it’s nutritionally balanced meals, more than 65 of them, “are all based on a similar design, so they are easily interchangeable and you’re assured of getting great nutrition every day.” These ‘meals’ are bars, shakes, soups, snacks, desserts and a few pasta entrees. 
You do need to, obviously, supplement with real food. Medifast has that part covered with its “lean and green” recipes, described as including 7 ounces of protein, 3 servings of vegetables, and up to 2 servings of healthy fats, the latter “depending on your lean protein choices.” The recipes are available to Medifast customers on their blog and in their cookbook. But they also sell individual Medifast ‘Flavors of Home Lean and Green’ meals. 
A 14-day Medifast diet meal replacement kit is $149 and includes an assortment of Medifast “meals” (70 total) that include shakes, snacks, and soups so I’m not sure if a shake constitutes a meal, but I am assuming it does. So you’ll get stuff like a pasta dish, brownies, chicken noodle soup, peanut butter crunch bars, vanilla shakes, and mashed potatoes. And you receive a welcome kit, food journal, dining-out guide and a plastic blender bottle. 
Similarly, the 30-day kit at $329 provides a month’s worth of Medifast Meals, 147 in total with dishes like the 14-day but it appears like you get more variety like oatmeal and pretzel sticks, but the list on the website appears to be mostly snack foods, shakes and a couple of side dishes, also known as meal replacement stuff. 
I decided to click almost all the way through as if I were ordering, when I saw the fine print: Medifast meals come auto-shipped monthly after the first month at the original full price of $429 charged to your credit card. Medifast makes it sound like you are getting an amazing deal what with free shipping (in all caps, twice) and its “rewards” program where you get discounts on future orders. It’s all very enticing, but once you click though, you’re enrolled: “By placing this order you are agreeing to these terms.” 
Yup, the Medifast meal kits will arrive every month, costing you nearly $5,000 for a year’s worth. You’re permitted to cancel at any time and I’m sure that you are able to or they wouldn’t be in business (we’ll see in the Word on the Street if that holds true) but still, it was not clear at all until I got to the last page where you enter contact and credit card information before I saw what was what. This tactic will affect my Bottom Line on Medifast, I can assure you. 
By the way, if you’re interested, know that Medifast coupon codes pop-up on the site, so if this diet is for you watch for them. While I was on the site, a code came up for 14 free meals. You can also find coupons online from sites like Groupon. 
Additionally, Medifast features a number of specialty diets, too—including weight management, and for people with specific conditions like diabetes and thyroid conditions, for example. Most of these are supposed to be medically supervised. 
Meals you make yourself based on strict “lean and green” Medifast recipes and of course, their dozens and dozens of meal replacement options from shakes to soups to snacks. 
The Science (or Lack Thereof) Behind Medifast
Two studies are most quoted about Medifast. The abstracts for both can be found in the vast journal article archive on the website of the National Institutes of Health (NIH). Let’s talk about the studies, and then I’ll tell you what the big problem is with both.
The first—published in the March 2011 Nutrition—was a 40-week randomized, controlled clinical trial with 90 obese adults randomly assigned to one of two weight loss programs for 16 weeks, and the same program followed for a 24-week period of weight maintenance. The first weight loss program was Medifast’s meal replacement program and the other was a “self-selected, isocaloric, food-based meal plan.”
According to the findings of the 2009 study,
“the meal replacement diet plan evaluated was an effective strategy for producing robust initial weight loss and for achieving improvements in a number of health-related parameters during weight maintenance, including inflammation and oxidative stress, two key factors more recently shown to underlie our most common chronic diseases.” 
Wow. Sounds good.
A second study—published in the December 2013 International Journal of Obesity (London)—had 120 obese men and women participating in a randomized, controlled trial with half on the Medifast meal replacement diet and half on an equally low-calorie food-based diet. At 26 weeks, the people on Medifast lost 16 pounds versus almost 9 pounds for the other group.
“In obese adults, (a meal replacement diet) resulted in significantly greater reductions in body weight and fat compared with an (food-based) diet for 1 year after randomization.” 
I actually found another, this one published in the 2015 Nutrition Journal : “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.” That’s a mouthful. This study also found “achieving clinically meaningful weight loss and preserving lean body mass in a broad population of overweight and obese adults.” 
So here’s the problem with all of these officially and federally registered clinical trials: they are all “investigated,” funded, supported, written, carried out and essentially, bought and paid for by Medifast. Every single one.  
If you scroll down to the bottom, you’ll see one study’s co-author, Linda M Arterburn, is not only a Medifast employee (like the study author Linda Davis from the first clinical trial) but controlled “all aspects of this study.” And she was joined by other Medifast staff where “competing interests” are disclosed and you find out that all the authors of the study are employees, receive salaries from Medifast, and Medifast paid them and covered all study costs. Same with the other two research studies that found a Medifast diet results in “clinically meaningful” and “significant weight loss.” But Medifast authored all the studies, though you really have to dig deep to find that out.
The question, I suppose, is this: is that a bias? Bought-and-paid-for studies? I’m not saying they aren’t legit, but I am not comfortable with it. Does it make a difference to you?
Here’s one study from Vanderbilt University which examines VLCDs that sub out meals for liquids (meal replacement shakes, soups, etc.) and mentions Medifast. Its bottom line? For very obese patients, liquid or VLC diets can cause a large amount of weight loss—but unless medically directed and supervised, they can be “misused and lead to health risks.” 
The Vanderbilt study also cautions that overweight or mildly obese people try out lots of diets, including meal replacement or ones where you eat a few hundred calories a day and,
…the more one diets, the slower one’s metabolism becomes; therefore, one must eat less in order to maintain one’s weight.  (emphasis added)
Now that makes sense to me. Plus, Vanderbilt researchers say one must—for safety and for the sake of effectiveness—seek medical help before starting a meal replacement, liquid or VLCD. 
Word on the Street about Medifast
What about Medifast reviews? Since Medifast is so well-known and such a powerhouse in the diet world, I went straight to Consumer Reports for Medifast reviews, all of which appear quite candid and legitimate. Since 1936, Consumer Reports, a non-profit organization, has been providing “unbiased product ratings and reviews.” So this is one of the best sites to get the real deal.
Based on 140 ratings from just about 250 reviews, Medifast earned a 4-plus star rating out of 5 stars. Review after review, Medifast gets all the stars. People rave that it works miracles with weight loss; you will lose weight. 
The most recent review was from just a couple of days ago, August 2017. “Kyleigh,” who gave Medifast 4 stars, says she was introduced to Medifast through an online video.
I saw a video on YouTube of someone reviewing their experience with Medifast. It seems like a way that I could cut back on calories but still get the nutrition that I needed because it had all the vitamins and minerals. My experience going through the diet started off well and I was surprised by how good a lot of the meals tasted. But then as the diet progressed, it got really monotonous eating the same things over and over. I didn’t experience any more weight loss with this program than I would if I just changed my diet. I think the results are overstated in a lot of the publicity and that was the biggest drawback for me. I really like that it was convenient, but it wasn’t quite what I expected. The only interaction I had with the team was when I called to stop my subscription, and they were very helpful. 
But a common theme I found was that a number of people, while giving it high marks as very effective for extreme weight loss, caution that it’s difficult at best to sustain it and many gain some or all of the weight back once they go off the diet.
“Milena” (Aug 2017, 5 stars) posted very recently that you have to stay with it and make it a “priority over everything.”
Medifast was suggested by our primary physician. It seemed like an easy way to lose weight. The difficult part for me with every diet is to figure out what I can eat. With Medifast, that decision was easy to make and that’s why we chose it. I order online and everything arrives on time. The diet is reasonable. I love it. The meal bars can be used for snacking and it’s good tasting so I like it. When I first tried it nine years ago, it worked very well. I lost 50 pounds and my husband lost 90. So, it was very good. But lately, I was out of control. In order for this to work, it’s helpful if you can make it the most important thing for you to lose weight and it should take priority over everything. We lost a lot of weight after this and then we gained again two years after that. We tried several times and without so much success. If you try to do it just hoping that eating the meal will help, it’s not working. It needs dedication very much. 
I went in search of very negative reviews, too—1- and 2-star reviews—and found 80 reviews; some were frightening, with users listing serious health problems occurring post-diet. It’s not clear how many of these people consulted a doctor before starting the diet. Nonetheless, let that stand as a warning: ask your doctor before you start Medifast.
Also, I want to point out that the most worrisome of the reviews listing serious side effects are, for the most part, from 2010 to 2013 and we know that the product was, at the least, renamed. Not sure about formulations. In any event, these two reviews represent the problem people have with Medifast: the food is not palatable and have concerning side effects.
“Nicole” (Mar 2017, 1 star) says,
I have friends that tried Medifast and I wanted to try it myself. I followed the diet to the letter and it was not good. The food was inedible and it was too hard to swallow. I was able to choke it down, but I’d rather lose weight slowly than have to be miserable with what I’m putting in my body. Although I liked the bars and they tasted like a regular Granola bar. They also didn’t pressure me when I went to cancel, which was nice. Overall I’m a bit irritated that I wasted money. 
“Lourdes” (Jan 2017, 1 star) says,
I was on Medifast for close to a year. My goal weight to lose 17 pounds. I was unable to stomach the food so I lived on shakes and bars. Barely edible. I felt like I was always starving and the snacks were not helping. Aside from the bloating and loose stools they warn you about, I was always dizzy, had nausea and felt like I was going to pass out. If I caught the smell of real food, it would trigger terrible hunger pangs. I understand that this diet has been very successful with others but it did NOT work for me. My total weight loss after starvation because that is what it felt like plus exercising 5-7 days a week while on the diet only yielded a 10 pound loss over 6 months. Within 4 months I gained it all back and 6 months after that I put on a total of 30 pounds.
Never have I been this heavy and honestly my internal medicine doctor believes it screwed up my metabolism. So I am using real food, clean food, drinking lots of water and going to the gym. The results may be slower BUT I no longer have the awful side effects or hunger pangs and food craving. I also paid for the weekly coach in case anyone is wondering and followed this diet to the letter. No cheating. She was a nice young lady but gave a lot of rehearsed answers out of the playlist and for me it was a waste because it felt like one size fits all. The poor girl did not have much to add since there were no gaps in my process. But congratulations for the people for whom this works. 
The Bottom Line: Is Medifast Worth a Try?
Risky (mid-level risk). It’s a restrictive diet of far less than what’s universally recommended for proper nutrition and appropriate caloric intake. It is, simply put, a very low calorie diet. But one that requires Medifast brand meal replacements, including Medifast shakes, Medifast bars, Medifast snacks, and more.
I’m not a fan of prepackaged food diet food, no matter how much nutrition is said to be packed in there. It is still processed in some manner, and processed foods—especially “diet” processed foods—may contain hidden junk that some nutritionists claim may sabotage weight loss. Just saying.
And, Medifast is super-expensive at $300 to $400 a month (and that’s before your regular family grocery bill.) So it’s unsustainable in the long term, is often pushed by MLM distributors, and is just far too costly.
That said, if your doctor recommends it—or if you ask and your doctor approves—go for it. But know up front, unless you change your eating habits and incorporate regular and energetic exercise into your life for good, you won’t keep that weight off once you go off the plan. But it’s your call.