The Medifast diet — which has been replaced by an offshoot program, Optavia — is a weight-loss plan that promises to help you shed pounds easily with its branded snacks and meals. But the reality may look a little different, which is why it's important to be aware of potential Optavia side effects.
Here's everything you need to know about the side effects of the Optavia diet to help you decide if it's worth trying. (Of course, talk to your doctor before trying this or any weight-loss program to make sure it's safe for you, according to the Mayo Clinic.)
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It's worth noting that in April 2022, a class action lawsuit was filed against Optavia over claims that the company enrolled customers in its auto-shipment program without consent to do so. The lawsuit also claims that Optavia is a multi-level marketing company that recruits consumers as "coaches", according to ClassAction.org.
What Are Medifast and Optavia?
Medifast was founded in 1981 as a meal replacement weight-loss program that provided pre-made snacks and meals to dieters, according to the company's website.
The company has since phased out Medifast and launched Optavia, so if you're wondering what happened to Medifast shakes, that diet is no more. Optavia instead offers a manifold approach to weight loss, per the website. The program includes:
- Meal replacements and snacks called Fuelings
- A "Habits of Health" program that helps you make small behavioral changes to support wellbeing
- Access to a health and wellness coach
- Access to other members of the Optavia community
Optavia encourages followers to eat six meals a day, some of which are their Fuelings products and others that are "Lean & Green" meals you make yourself, according to the Optavia website. It also suggests avoiding alcohol, sugary drinks, shortening and other high-calorie foods.
The Fuelings snacks (think: shakes, soups, bars and biscuits) are low in carbs and calories, high in protein and contain added probiotics, per the website. The low-calorie "Lean & Green" meal contains lean protein, starchy veggies and beneficial fats, according to the website.
There are three plan options:
- 5&1 plan: Five Fuelings and one "Lean & Green" meal daily
- 4&2&1 plan: Four Fuelings, two "Lean & Green" meals and one snack per day
- 3&3 plan: Three Fuelings and three "Lean & Green" meals each day
Is Optavia a Ketogenic Diet?
While some people think that Optavia is a ketogenic diet because it is low-carb, it is not an official ketogenic diet because it does not have a higher fat content over carbohydrate content in its Fuelings and "Lean & Green" meals. A ketogenic diet (which was originally created to help children manage epileptic seizures) requires 90 percent of your calories per day to be fat sources, per Harvard Health Publishing.
Who Should Avoid the Optavia Diet?
Optavia may not be ideal for people with cancer, liver disease, kidney disease, an eating disorder or those who are taking medication for diabetes, high blood pressure, blood clotting or bipolar disorder, according to U.S. News & World Report.
Additionally, the Optavia website says sedentary, older adults or those who exercise more than 45 minutes per day should avoid the Optimal Weight 5&1 plan. If this sounds like you, talk to your doctor before trying this or any diet program.
What Are the Side Effects of Optavia?
Negative Medifast reviews criticized the diet for red flags like promises of fast weight loss and its extensive use of supplements to replace whole foods, according to the University of Utah Health. And Optavia reviews cite certain side effects that are similar to these Medifast risks.
That said, how safe is the Optavia diet? Here are the possible side effects:
1. It May Not Provide Adequate Calories
One Optavia diet side effect is that the program may not provide your body with enough calories, according to U.S. News & World Report.
Fuelings snacks are low in calories, typically clocking in around 90 to 120 calories per serving. And "Lean & Green" meals are usually about 300 calories per serving, per the website. Altogether, that can amount to eating as few as 800 to 1,000 calories calories per day, putting your body in starvation mode, according to U.S News & World Report.
And while this drastic calorie cutting may lead to speedy weight loss, shedding pounds that quickly isn't safe or sustainable (more on why in a moment). Per the Mayo Clinic, losing 1 to 2 pounds per week is the safe, expert-recommended pace of weight loss to aim for in order to give your body the fuel it needs to function at its best.
Though it doesn't specify if these symptoms are due to calorie restriction, according to U.S News & World Report, Optavia side effects may include:
- Loose skin
- Hair loss
- Leg cramps
- Bad breath
- Menstrual changes
Calorie intake should not fall below 1,200 per day for people assigned female at birth or 1,500 per day for people assigned male at birth, except under the supervision of a doctor, per Harvard Health Publishing.
2. It May Not Provide Adequate Nutrients
Similarly, another potential Optavia side effect is that not eating enough calories can deprive you of essential nutrients, according to Harvard Health Publishing.
What's more, the diet requires you to replace many — if not the vast majority — of your meals with replacement products (Fuelings). According to the Mayo Clinic, it's almost always better to eat plant-based foods rather than these supplemental snacks or ultra-processed foods, as meal replacements often can't provide the same nutritional benefits as natural foods.
And if you don't get the nutrients you need, there can be health consequences. According to Rush, you can develop vitamin and mineral deficiencies (including vitamins A, B, C, D, E and K and minerals like potassium and magnesium) that may cause the following symptoms:
- Hair loss
- Burning sensation in your feet or tongue
- Slow-healing wounds
- Bone pain
- Vision problems
- Irregular heartbeat
Visit your doctor if you show any of these symptoms, as they can help diagnose and treat your nutrient deficiency, according to Rush.
3. It Can Lead to Muscle Burn
Severely cutting calories can not only deprive you of nutrients — it can also lead to muscle loss, according to the Mayo Clinic. That's because your body tends to burn through water weight and lean tissue before fat in response to eating an extremely low-calorie diet.
It's recommended to eat enough protein and get enough physical exercise (like resistance-type training) to preserve muscle mass and strength while on a low-calorie diet, according to a May 2017 review in Advanced Nutrition.
4. It May Lead to Weight Regain
About 90 percent of people who lose a significant amount of weight eventually regain about all of it, per the University of Michigan Health. While Optavia can lead to short-term weight loss, it may not be the best program for keeping those pounds off in the long haul.
That's why weight regain is one of the potential long-term side effects of Optavia.
There are a few reasons for this: First, severely cutting calories signals your body to decrease your levels of a hormone that promotes feelings of fullness while also increasing your levels of an appetite-stimulating hormone, per the Cleveland Clinic. In other words, you'll feel hungrier after eating a typical serving, which may encourage eating more than usual and, as a result, weight gain.
Dieting may also negatively affect your metabolism, which can lead to weight regain after a calorie-restrictive diet ends, according to the Cleveland Clinic.
The best way to lose weight safely and sustainably is to eat a diet full of nutritious whole foods, exercise regularly, get good sleep and manage stress, per the Cleveland Clinic.
5. It Can Cause Digestive Problems
Some dieters have reported digestive symptoms like gas, constipation and diarrhea on Medifast or Optavia, according to U.S. News & World Report.
These issues may be caused from two key ingredients in Optavia shakes — xantham gum and carrageenan gum. Both are safe food additives, but have been associated with gas and bloating in people with irritable bowel syndrome, per the University of Arizona Health.
Some people also experience digestive upset from whey or soy protein isolate — ingredients found in Optavia's Fuelings.
6. It Can Cause Gallstones
According to U.S. News, the Optavia diet can cause gallstones (hard clumps of digestive fluid in the gallbladder) for those already at risk.
You're at a higher risk of getting gallstones if you participate in crash diets (which can disturb the normal balance of cholesterol and bile in your liver), have obesity or are between the ages of 20 and 60 and assigned female at birth, per U.S. News.
Some people think the Optavia diet causes kidney stones, but there is not enough evidence and research to support this claim.
7. It Can Put You at Risk for Eating Disorders
Apart from causing long-term weight gain, dieting can also put you at risk for developing an eating disorder, according to a September 2020 review in The Cureus Journal of Medical Science. It can also be triggering for those who've experienced an eating disorder in the past.
The limitation of certain foods/food groups and significant calorie restriction on the Optavia diet can cause dieters to continue harmful behaviors well past their chosen diet plan.
8. It Can Be Costly
While not an Optavia side effect per se, another common complaint is the cost of the program, which can run about $400 to $450 for three weeks' worth of food, according to U.S. News & World Report. That doesn't include the cost of additional groceries for your homemade "Lean & Green" meals.
Does Medifast Cause Cancer?
There's no evidence to show that this diet is linked to cancer. There are likewise no Medifast diet customer reviews establishing a link between the two.
Can the Optavia Diet Help You Lose Weight?
While the Optavia diet can help you lose weight quickly in the short term, it's not likely to help you maintain that weight loss long term.
While an August 2015 review in Nutrition Journal found Medifast clients with obesity lost about 24 pounds in 12 weeks, an April 2015 report by Johns Hopkins Medicine found little evidence that users of commercial weight-loss programs (like Medifast) lost more weight over time than those who didn't use them.
How Long Should You Stay on Optavia?
Optavia only features plans that last up to 12 weeks. Very low calorie and low-calorie diets should only be followed for a maximum of 12 weeks and under the supervision of your doctor, according to the NHS.
Bottom line: Focusing on safe, healthy, long-term weight-loss goals can be more effective for your health and weight.
- Medifast: "About Us"
- Optavia: "We are Optavia"
- Optavia: "What is a Fueling?"
- Optavia: "What is a Lean & Green meal?"
- University of Utah Health: "Ranking Popular Diets"
- Harvard Health Publishing: "Calorie counting made easy"
- Mayo Clinic: "Weight loss basics"
- Mayo Clinic: "Supplements: Nutrition in a pill?"
- Rush: "6 Signs of Nutrient Deficiency"
- Cleveland Clinic: "Why People Diet, Lose Weight and Gain It All Back"
- Mayo Clinic: "Weight loss: Choosing a diet that's right for you"
- U.S. News & World Report: "Does OPTAVIA have any health risks?"
- U.S. News & World Report: "What Is OPTAVIA?"
- Medifast: "Medifast Direct"
- Harvard Health Publishing: "Should you try the Keto Diet?"
- Advanced Nutrition: "Preserving Healthy Muscle during Weight Loss"
- University of Michigan Health: "Weighing the Facts: The Tough Truth About Weight Loss"
- University of Arizona: "Irritable Bowel Syndrome: Diet and Stress"
- 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"
- Johns Hopkins Medicine: "Few Commercial Weight-Loss Programs Show Reliable Evidence of Effectiveness, Johns Hopkins Reports"
- NHS: "Very low calorie diets"
- The Cureus Journal of Medical Science: "Have Our Attempts to Curb Obesity Done More Harm Than Good?"