© (Getty Images)Overhead view of russet potato, purple potato, and sweet potaot
Single food, or monotrophic, diets - also called mono diets - have been around for as long as the diet industry itself. Often touted as miracle quick fixes, these diets are severely restrictive and potentially dangerous.
"A monotrophic diet is a type of fad diet that dictates eating only one food item for extended periods of time with the main goal of losing weight," says Janine Souffront, health educator supervisor for L.A. Care Health Plan, the largest publicly operated health plan in the country.
Examples of a Mono Diet
Some common foods that have been targeted for monotrophic diets over the years include:
Stacey L. Pence, a registered dietitian at the Ohio State University Wexner Medical Center in Columbus, says any food or food group can become the focus of a monotrophic diet - think the grapefruit diet, an all-meat diet like the carnivore diet or the all-fruit diet. "There are many variations on the mono diet," and most people who adopt this approach are using it as a means of jump-starting weight-loss efforts.
Souffront notes that some "bodybuilders choose to eat just protein, such as eggs or chicken breast, under the false belief that it will help build muscle and keep body fat down."
Are Mono Diets Healthy?
In short, no. "This type of diet is never a good idea," Souffront says. "It's one of the most extreme diets, with no chance of long-term success but with many chances for causing health problems."
Pence agrees. "I can't think of any good reason to recommend a mono diet to a healthy adult or someone with chronic health issues."
Monotrophic diets can put you at risk for certain health consequences, including:
Nutrient Deficiencies
Relying on just one food for sustenance "can cause nutrient deficiencies." No single food item can offer "a complete balance of all the macro or micronutrients our bodies need. Too much of any one food or nutrient is not a good thing." And Pence adds that "you may feel sluggish and tired without getting proper balance of nutrients."
Loss of Muscle Mass
A loss of muscle mass brings with it a reduction in metabolism, Souffront says, and this can make losing weight even more difficult. Lean muscle burns more calories than other types of body mass, and if you lose lean muscle mass, your metabolic rate can decline.
Nutrient Toxicities
On a monotrophic diet, you may ingest dangerous levels of other nutrients when you eat just one type of food. "For example, eating only chicken breast will cause a vitamin C deficiency, among others, while the excess protein may cause kidney problems.
Eating only bananas will result in excessive carbohydrate intake that can negatively challenge the pancreas and excessive potassium intake that can cause an irregular heartbeat," Souffront says.
While not all nutrient excesses are dangerous, some can be noticeable and unpleasant all the same. "For example, if you chose an all carrot diet and ate excessive amounts of carotene contained within carrots and your skin starts to turn yellow-orange," Pence says.
Mental Health Impacts
Monotrophic diets can set the stage for an eating disorder, Souffront says. "Eating with such restrictions is toying with disordered eating. It can lead to food moralizing, the labeling of foods as 'good' and 'bad.' It can also lead to feeling deprived, with its consequence, the damaging overeating-guilt cycle. Denying the body and mind the satisfaction of eating a variety of foods can even lead to the worsening of anxiety, depression and mood problems."
Rebound Weight Gain
And when it comes to keeping the weight off long term, monotrophic diets are simply not sustainable, Souffront says. "If you're only eating one food, even if it's your favorite food, you'll get tired of eating it after a while. This flavor fatigue can lead you to stop eating to achieve weight loss or propel you into overeating. This is dangerous and you're bound to re-gain any weight lost and then some."
Why Are Mono Diets so Popular?
In a word: simplicity. Dieting for weight loss can be confusing, and finding the right balance of foods to help shift excess weight can be a complex and frustrating undertaking. Monotrophic diets promise to alleviate a lot of that challenge. "Only eating one type of food daily leaves out the guesswork on what to prepare for meals and it's easy to follow," Pence says.
And because there's no food logging, carb calculating or calorie counting required, that absolves the dieter of much of the work that other approaches to weight loss rely on. Monotrophic diets "require no thinking, calorie awareness or food preparation," Souffront adds.
The problem, though, is that once you leave the monotrophic diet - which you will eventually have to do if you want to avoid malnourishment - you won't have learned any sustainable skills for maintaining the weight loss, and you're likely to regain all the weight you lost. "You may achieve weight loss with this diet but increase your risk for nutrient deficiencies which is not a healthy way to reach your weight goals," Pence says.
Additionally, the fad-like nature of these diets is easy to promote. "With social media's ability to mainstream pseudoscience, there are plenty of people promoting this way of eating, preying on the human tendency to want shortcuts," Souffront says.
The bottom line, she says, is "if it sounds too good to be true, it most likely is. There's no substitute to having a balanced approach to eating that promotes a healthier weight long term."
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