8 Optavia Side Effects to Consider Before Trying the Diet
By
Kathleen Ferraro
Updated on August 6, 2025
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The Medifast diet — which Optavia, an offshoot program, has replaced — 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. Consult your doctor before attempting this or any weight-loss program to ensure it's safe for you. It's worth noting that in April 2022, a legal team filed a class action lawsuit against Optavia over claims that the company enrolled customers in its auto-shipment program without consent to do so. The lawsuit also maintains that Optavia is a multi-level marketing company that recruits consumers as "coaches".
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. Optavia instead offers a multifaceted 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 they prepare themselves, 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 website also advises that low-calorie "Lean & Green" meals consist of lean protein, starchy vegetables, and beneficial fats.
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 than 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 come from fat.
Who Should Avoid the Optavia Diet?
People who have or have had the following illnesses should consult with a doctor before trying an Optavia program:
- Cardiovascular disease, including heart attack
- Diabetes
- Cancer
- Thyroid disease
- Liver disease
- Kidney disease
- Eating disorders such as anorexia or bulimia
- Other conditions that require medical care or that weight loss may affect
The Optavia website says the following should avoid the Optimal Weight 5&1 plan:
- Sedentary older adults
- People who are breastfeeding
- People who have gout
- People with type 1 diabetes
- Teens, as a teen-specific plan called the OPTAVIA for Teens Plan is available
- People who exercise more than 45 minutes per day
If this sounds like you or you have any special dietary or medical needs, talk to your doctor before trying this or any diet program.
What Are the Side Effects of Optavia?
In the past, 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. And Optavia reviews cite certain side effects that are similar to these Medifast risks.
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. Fuelings snacks are low-calorie, typically clocking in around 90 to 120 calories per serving at an average of just over 105 kcal. And meals in the Optavia "Lean & Green" cookbook usually contain anything from 260 to 400 kcal per serving, averaging at 347 kcal. Altogether, that can amount to eating as few as 710 to 950 calories per day, putting your body in starvation mode.
And while this drastic calorie cutting may lead to speedy weight loss, shedding pounds that quickly isn't safe or sustainable. Losing one to two pounds per week is the safe, expert-recommended pace of weight loss to aim for, as it allows your body to receive the necessary fuel to function optimally.
Though it doesn't specify if these symptoms are due to calorie restriction, Optavia side effects may include:
- Gallstones or gallbladder disease
- Temporary hair thinning
- Muscle loss
- Dizziness
- Lightheadedness
- Headache
- Fatigue
Seek immediate medical attention if you notice the following symptoms:
- Muscle cramps
- Tingling
- Numbness
- Confusion
- Rapid or irregular heartbeat
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.
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.
The diet also requires you to replace many — if not the vast majority — of your meals with replacement products (Fuelings). 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 necessary nutrients, you can experience health consequences. You might 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.
3. It Can Lead to Muscle Burn
Severely cutting calories can not only deprive you of nutrients — it can also lead to muscle loss. That's because your body tends to break down muscle in response to eating an extremely low-calorie diet.
Increasing the proportion of calories derived from protein, combined with regular physical exercise (such as resistance training), can help preserve muscle mass and strength while following a low-calorie diet. However, increasing the proportion of protein while on an excessively low-calorie diet (under 800 calories daily) may still not reduce muscle loss, per a 2021 randomized controlled trial.
4. It May Lead to Weight Regain
Approximately 80 to 85 percent of people who lose a significant amount of weight eventually regain most, if not all, of it. 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 the Optavia program.
There are a few reasons for this: First, severely cutting calories signals your body to decrease your levels of hormones responsible for appetite control. Your body may be telling you to eat more due to the low intake of calories.
Dieting may also negatively impact your metabolism, causing your body to burn calories more slowly. This can make it easier to lose weight upon resuming a full-calorie diet.
The best way to lose weight safely and sustainably is to eat a diet full of nutritious whole foods, exercise regularly, set attainable goals, and work on maintaining a good mindset.
5. It Can Cause Digestive Problems
Some dieters have reported digestive symptoms like gas, constipation, and diarrhea on Medifast or Optavia.
These issues may be caused by two key ingredients in Optavia shakes — xanthan gum and carrageenan gum. Both are safe food additives but have links to gas and bloating in people with irritable bowel syndrome.
Some people also experience digestive upset from whey or soy protein isolate in people with certain intolerances or allergies. Both of these are ingredients in Optavia's Fuelings.
6. It Can Cause Gallstones
The Optavia diet can cause hard clumps of digestive fluid in the gallbladder, known as gallstones, in individuals who are already at risk, such as people assigned female at birth or those with overweight or obesity.
Crash diets lead to a higher risk of getting gallstones. They can disturb the normal balance of cholesterol and bile in your liver.
7. It Can Put You at Risk for Eating Disorders
Dieting can also put you at risk for developing an eating disorder, according to a review.It can also be triggering for those who've experienced an eating disorder in the past.
The limitations of certain foods/food groups, as well as significant calorie restriction, on any extremely low-calorie diet, including an Optavia program, can cause people to continue potentially 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 range from $385 to $430 for three weeks' worth of food, depending on the plan chosen.
That doesn't include the cost of additional groceries for your homemade "Lean & Green" meals.
Can the Optavia Diet Help You Lose Weight?
While the Optavia diet can help you lose weight quickly in the short term, it's unlikely to help you maintain that weight loss in the long term.
A 2021 review of randomized controlled trials found that individuals on Medifast and Optavia lost 4.2 to 7.8 percent of their body weight after 12 months, which was greater than that of the control group. And presentation notes in the European Medical Journal highlight that Optavia’s partial meal replacement regimen, combined with coaching calls, resulted in better weight loss and adherence to the plan than some other alternatives — but it was Optavia running the study.
Neither of these studies assessed Optavia’s long-term weight loss impact. A review found that studies generally suggest that people regain around 40 to 50 percent of the weight they lost within one or two years without follow-up treatment.
How long should you stay on Optavia?
Optavia only features plans that last up to 12 weeks, although the review above showed efficacy and safety up to 12 months. You should only follow very low-calorie and low-calorie diets for a maximum of 12 weeks and under the supervision of your doctor.
Takeaway
- If you're considering the Optavia diet, be aware of potential side effects, including gallstones, nutrient deficiencies, digestive issues, and muscle loss. These symptoms require close monitoring and might need medical attention.
- Although rapid weight loss can occur with this diet due to severe calorie cutting, it's important to note the lack of evidence supporting long-term success and the high risk of weight regain.
- Consider seeking consultation with a healthcare provider before starting the program, especially for those with underlying health conditions or a history of disordered eating, due to the extreme calorie restriction and potential health risks involved.
- Focusing on safe, healthy, and long-term weight management goals can be more effective than adhering to regimented, expensive diet plans for meeting your health needs.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
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Kayli Anderson, RDN
Medical Reviewer
Member of American College of Lifestyle Medicine
Kayli Anderson has over a decade of experience in nutrition, culinary education, and lifestyle medicine. She believes that eating well should be simple, pleasurable, and sustainable. Anderson has worked with clients from all walks of life, but she currently specializes in nutrition therapy and lifestyle medicine for women. She’s the founder of PlantBasedMavens.com, a hub for women to get evidence-based, practical, and woman-centered guidance on nutrition and cooking, hormone health, fertility, pregnancy, movement, mental well-being, nontoxic living, and more.
Anderson is board-certified in lifestyle medicine and serves as lead faculty of the American College of Lifestyle Medicine’s (ACLM) "Food as Medicine" course. She is past chair of the ACLM's registered dietitian member interest group, secretary of the women's health member interest group, and nutrition faculty for many of ACLM's other course offerings. She is the coauthor of the Plant-Based Nutrition Quick Start Guide and works with many of the leading organizations in nutrition and lifestyle medicine to develop nutrition content, recipes, and educational programs.
Anderson frequently speaks on the topics of women’s health and plant-based nutrition and has coauthored two lifestyle medicine textbooks, including the first one on women’s health, Improving Women's Health Across the Lifespan.
She received a master's degree in nutrition and physical performance and is certified as an exercise physiologist and intuitive eating counselor. She's a student of herbal medicine and women's integrative and functional medicine. She lives with her husband in the Colorado Rocky Mountains, where you’ll find her out on a trail or in her garden.