The start of the new year often brings fitness resolutions, including wanting to change up one’s diet in order to “lose those last 10 pounds.” With the rise in popularity of keto and paleo diets, you too might be considering jumping on the fad diet bandwagon. After all, you’ve probably seen those after pictures; they seem to work, right? Maybe. But at what cost?
“Many fad diets are popular because they may produce a weight decline in the short term. However, realistically, they do not result in a long-term success for weight loss. They often are unhealthy, and some can severely jeopardize your health,” Carol Aguirre, a registered dietitian, tells SheKnows.
So how exactly can fad diets be more harmful than helpful? We asked some experts to weigh in on the realities of these trendy eating plans.
First of all, it’s important to note that not all diets are created equal. But when you’re significantly restricting what you’re eating, you’re bound to be short of some key nutrients.
“It depends on the diet, but cleanses and hard-elimination diets can cause nutritional deficiencies that can affect energy levels and mental health,” physician and researcher Dr. Seema Marwaha tells SheKnows. “You can be nutrient- or calorie-deficient as well. The main concern with a diet that calls for eliminating entire food groups is that you’re missing out on the key nutrients in those foods.”
Take the keto diet, which is super-low-carb and high-fat, for example. According to Marwaha if you reduce your carb intake by skipping grains, fruits and vegetables, you’ll fall short on fiber, antioxidants and possibly vitamins like A and C and minerals like magnesium and potassium. You’re going to want those.
They can lead to disordered eating
Because fad diets often promote short-term results and unhealthy eating habits (you can’t eat certain food groups, for example, or you can only eat at certain times of the day), they can lead to disordered eating.
“Often, with fad diets, there are rules dictating ‘good foods vs. bad foods,’ strict routines and a social component that may provide motivation but also could increase embarrassment for those who don’t ‘succeed’ or follow through,” says Aguirre. “In many cases, supporters of a fad diet will connect improved physical and emotional health, increased confidence and self-esteem and improved body image.”
These promises are enticing but unrealistic, says Aguirre, and failure to achieve these goals can lead to disappointment. She notes that not everyone who tries a fad diet develops an eating disorder, and many develop eating disorders in the absence of these trends, but “it is important to make considerate decisions about lifestyle changes, to consider the vulnerabilities and risk factors and be aware of warning signs that [you] may be headed toward an eating disorder.”
They mess up your metabolism
Your gut and metabolism take about three weeks to adjust to new foods, says Marwaha, which means if you’re trying a new diet every month, your body is constantly playing catch-up, and that can be hard on your system.
“When you jump from one diet to another, your daily intake can start to swing,” she says. “Even if you stick with one diet for months, you could end up consuming 2,000 calories one week and 1,200 the next without realizing it.
That fluctuation is a problem. If your energy consumption isn’t consistent, it can slow down your metabolism, so you end up gaining weight.” It can also change your hunger cues, leaving you irritable.
They make you too tired to exercise
Fad diets can definitely make you tired if you’re not giving yourself the proper nutrients you need to stay focused throughout the day. “Your body is like a car when it comes to needed fuel, and if you’re putting the wrong stuff in it or nothing at all, then you’ll be running on empty,” Jen Cohen, personal trainer and author of Badass Body Goals, tells SheKnows.
Not only will this slow down your body’s metabolism in an effort to conserve what little fuel it has, but Cohen says, “If you work out, then you have to replenish your body, and exercise is just as important as what you put into your body. The problem is you just have to make sure you’re putting things in your body.” If you’re running a low-calorie diet, then chances are you won’t even be able to make it through a workout.
They have long-term health effects
Weight fluctuation, even while in a healthy weight range, can negatively affect your cardiovascular health and life span, according to a 2017 study in the New England Journal of Medicine.
“A recent study out of Korea that looked at weight variability in people with ‘normal weights’ found that weight variability, in addition to diabetes, blood pressure and cholesterol, contributed to increased cardiovascular events and death,” says Marwaha. “This study suggests that the trends over time for weight, blood pressure, blood sugar and cholesterol are just as important as the numbers themselves when it comes to risk.”
Marwaha says this means people as well as their doctors should keep in mind that stability of numbers might be just as important as the numbers themselves. Someone who yo-yo diets will have an unstable range, which could lead to heart attacks or strokes.
Essentially, when it comes to healthy weight loss, the experts agree: Incremental changes work best.
“If you’re concerned about losing weight and improving your health, talk to a registered dietitian about developing a diet and exercise plan that’s right for you,” says Aguirre. “Healthy weight loss requires long-term lifestyle changes — not the quick and easy fix of a fad diet.”