Editor’s note: This article was updated to reflect the importance of medical supervision for some weight loss programs.

We all have that friend who jumps on the latest diet bandwagon and swears by it… until the next trend comes along.

Don’t be tempted to stop and start trendy diets if you’re trying to lose weight.

“Fad diets aren’t sustainable,” said Ashley Short, a Marshfield Clinic Health System registered dietitian. “You will likely regain the weight you have lost.”

5 ways to spot a bad diet

How do you know if a diet is just a fad that you should skip? If it has any of these traits, it’s not worth your time.

1. It promises fast weight loss.*

“Skip any diet that promises you’ll lose a pound or more a day,” Short said.

One or two pounds per week is a healthy rate of weight loss. You’re more likely to keep weight off if you lose it slowly. People who lose weight faster are more likely to gain it back.

2. Certain food groups are off limits.

Eating from all the food groups provides our bodies with essential nutrients. You miss out on important nutrients when you eliminate food groups, and these diets are hard to maintain.

The ketogenic, or ‘keto’ diet is an example of a recent diet trend that nearly eliminates an essential nutrient – carbohydrates. You’re advised to limit carbs to 10-15 grams per day, meaning you eat mostly protein and fats. The keto diet was originally intended to treat epilepsy in children only under the supervision of doctors and registered dietitians.

Carbohydrates are our main source of energy,” Short said. “You consume less fiber on a low-carb diet. Fiber helps you feel satisfied after eating and aids digestion. You may feel hungry or become constipated on a low-carbohydrate diet.”

Eating too much saturated fat increases bad cholesterol, which can negatively affect heart health. Eating too much protein may be hard on the kidneys over time. People who have chronic kidney disease should watch their daily protein intake and work with a registered dietitian to learn their daily needs and limits.

3. You must restrict food for a long time.*

You risk slowing your metabolism when your diet requires you to avoid eating or restrict calories for an extended period of time. Avoid diets that involve not eating for an entire day or limiting your calorie intake to less than 1200 per day.

People who follow restrictive diets may be at risk for developing eating disorders down the road.

“For those of you who are parents, you don’t want to teach your kids that eating very little or no food during the day is normal,” Short said.

4. It’s called a “cleanse.”

Some people believe colon cleansing improves health by removing toxins, boosting energy and enhancing the immune system. However, there is no evidence colon cleansing produces these effects or is beneficial at all.

Colon cleansing can be harmful. It can cause cramping, bloating, diarrhea, nausea, vomiting, dehydration, rectal tears, infection and electrolyte imbalance, which can be dangerous if you have health problems like kidney or heart disease. Coffee enemas sometimes used in colon cleansing have been linked to several deaths.

5. Supplements play a starring role.*

“It’s better to get nutrients from whole foods than from shakes, bars and pills,” Short said. “Vitamins and minerals are better absorbed from their natural sources.”

Supplements can be expensive, processed foods can be high in sodium, and eating packaged foods doesn’t teach healthful eating habits after you stop the diet. Short said you should always talk with your doctor before starting any type of weight loss supplement.

“There may be interactions with other prescription medications you take,” she said. “An extensive review of your medical history should be done as well, before starting any prescription or over-the-counter supplements.”

*Some weight loss programs of these varieties are successful with medical supervision.

Focus on portions and balance instead

A healthful diet includes a good balance of nutrients and not eliminating food groups.

Pay attention to portion sizes. Make treats like ice cream a weekly reward instead of a daily occurrence. Incorporate regular physical activity to improve long-term health. Talk to your doctor about starting an exercise routine if you have existing health conditions or physical limitations.

“Losing weight is about patience and consistency,” Short said. “It takes time. You have to think about it as a permanent lifestyle change and not a temporary diet.”

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