How to Spot a Diet Red Flag

While many consumers at some point consider which diet is best for them, too many people don’t give a lot of thought to the possible negative aspects of different eating regimens, says Lisa D. Ellis, a registered dietitian in private practice in Manhattan and White Plains, New York. She’s also a certified eating disorder registered dietitian and a licensed clinical social worker.

Shot of an attractive young woman cooking at home

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“Diets are such a commonplace part of our culture that many people tend not to give a lot of thought to the downside of a potential diet,” she says. “Would-be dieters might be less mindful of possible red flags because they are intrigued by the hopeful claims made by proponents of some diets. As a nutritionist and nutrition therapist, my priority is that people have a well-balanced diet, and maintain a healthy relationship with food.”

What Does Red Flag Mean?

In the context of diets, a red flag is an aspect of the meal plan that signals you should stay away from it for any number of reasons — whether it’s unhealthy, lacking in proper nutrition, unlikely to be sustainable in the long run or harming your health in some way.

Some people don’t recognize diet red flags because no one talks about them, says Amanda Sauceda, a registered dietitian in Long Beach, California. “I think now we are starting to see a shift in the conversation around food and eating,” she says. “This makes it easier for people to have the information they need to make better-informed decisions for their health. People are starting to see that there is no one style of eating that will work for every single person.”

Whether your goal is weight loss, avoiding or managing diabetes, improving your cardiovascular health or some combination of these, it’s important to be aware of potential diet red flags.

Top Diet Red Flags

When you’re choosing a diet to fit your lifestyle, here are 13 diet red flags you should what out for:


Diet meal plans are usually designed to work for a wide variety of people, without promising a precise result. “If a meal plan is promising a specific outcome like losing 30 pounds in 30 days, you should run,” Sauceda says. “You can’t guarantee that your body will look or even feel a different way (after following a diet for a set amount of time). Everybody’s body is different.”


“Meal plans that encourage drastic reductions in calories or prolonged periods of starvation could contribute to weight loss, if that’s your goal,” says Sandra Arevalo, a registered dietitian who is the director of community health and wellness at Montefiore Nyack Hospital in Nyack, New York. “However, they aren’t healthy because they can cause tiredness, dizziness, malnutrition and/or nutrient deficiencies, among many other symptoms.”


If a meal plan is making you feel bad about yourself, “that’s a big red flag,” Sauceda says. “If a meal plan is focusing on all the ‘bad’ things you normally eat as a way to make their plan stand out, ditch that meal plan. This is a double red flag if the meal plan is also very low-calorie. Food isn’t good or bad, it just is, and your relationship with food matters. Meal plans should be a tool to help you make healthy changes.”

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When it comes to shedding pounds, there’s no silver bullet quick fix, says Anthony DiMarino, a registered dietitian with Cleveland Clinic’s Center for Human Nutrition. “Not one single product or plan will provide rapid weight loss or a quick fix,” he says. “Weight status is impacted by many factors and there is nothing simple about it. Any kind of quick-fix tends to be unsustainable over time. If it sounds too good to be true, it probably is. Sustainable weight loss will occur slowly over a long period of time.”


Researching diets and weight loss products takes years, DiMarino says. “Scientific breakthroughs are pretty rare. In addition, products and diets that show promising results may gain some publicity before they hit the shelves,” he says. “Therefore, ‘scientific breakthroughs’ tend to be a misnomer. Most diet plans use these claims to get your attention and usually because there is no formal research supporting them.”


Healthy dietary plans should be able to cover all your nutritional requirements without the need to purchase any supplements, cleansers, drops or pills.

“Foods are the main sources of all the nutrients, dietary fiber and water we need,” Arevalo says. “When you follow a well-balanced meal plan you will be able to cleanse, hydrate and meet your weight goals only with food.”


“Each food or food group provides an array of nutrients that are essential to our health,” Arevalo says. “If you eat too much of a food or food group you will be eating too much of the same nutrients and lacking on others. A well-balanced diet is able to provide all the needed nutrients and for that, we need to eat foods from all food groups.”

For example, “There are meal plans that call for avoidance of carbohydrates. Carbohydrates are the main source of calories for our diet. If we don’t eat carbohydrates our body will need to use other nutrients to make energy, which is not the ideal and could cause health issues such as kidney disease.”


If a meal plan focuses on rotating only a handful of foods, that’s a red flag. “This even applies to when the foods are ‘healthy’ because one of the cornerstones of a solid way of eating is variety,” Sauceda says. “Variety is important because there is no one food that will give you all the nutrition that your body requires. You want to make sure it includes all the food groups and has a variety of foods within each food group. Plus, variety is supportive of a healthy gut microbiome along with overall health.”


Some famous people stay in the news because they always seem to be mired in one controversy or another, DiMarino says. “They become and stay popular because they cause a stir. Weight loss companies leverage this concept,” he says. “They know customers will flock to their sites if a popular celebrity endorses their product. Unfortunately, many celebrities have zero training or credibility to endorse such products or plans. If a famous individual endorses a particular product they have no expertise in, I would recommend you look elsewhere.”


If a diet requires you to purchase all of your food, shakes and snacks from the company marketing the meal plan, that’s a red flag, says Lara Metz, a registered dietitian based in New York City. “What if you don’t have access to their products? What if you don’t care for the taste or they don’t agree with you?”


Food is meant for fuel and pleasure. “Where is the pleasure if you are always eating differently than your family or friends?” Metz says. “Diets that are so restrictive where you feel limited and unable to participate in shared meals, celebrations or something as simple as a family dinner can be a red flag.”


Diets that are uber-restrictive and require very specific ingredients and preparation to the point they cause anxiety about dining in a restaurant is a red flag. “This anxiety and restrictive behavior may cause an unhealthy relationship with food and will not lead to long-term success,” Metz says.


Some diets call for adherents to only eat certain foods and restrict others for a set amount of days, then switch it up with a different set of restrictions for another set amount of days, Ellis says. “Restrictive diets are red flags,” Ellis says. “Limited-time diets are red flags and specific (food) diets are red flags. Three red flags in one diet type is impressive.”