Searching for the perfect diet to help you get back in shape? Many of us yo-yo from one weight-loss trend to another in hopes of shedding extra pounds. But our time and effort might be better spent elsewhere. Even if some of these trendy diets do help you lose weight, they may leave you less healthy.
Here are five diets that are not worth your time, according to studies and health experts.
The blood type diet
In the 1950s and ’60s, research indicated that those with blood type O had a slightly reduced risk of developing heart disease—one study suggested as much as 11% lower. In the intervening years, other studies have suggested that certain blood types offer a lower risk of diabetes, reduced risk of coronary artery diseases, lower levels of low-density lipoprotein (LDL) cholesterol, and more.
In light of the research, Peter D’Adamo, ND, proposed that diet should be dictated by blood type. In 1996, D’Adamo published a book arguing that those with blood type A should eat primarily fruits, vegetables, and grains; those with type O should focus their diet around meat, and those with other blood types should adjust their diets with other specifications.
But is there evidence that the blood type diet actually works? According to a study published in the Journal of the Academy of Nutrition and Dietetics in December 2020, the answer is no.
Researchers examined a cohort of 68 overweight individuals who were assigned either to a vegan diet, the blood type diet, or no diet, for 16 weeks. The primary outcomes measured were cardiometabolic changes, including body weight, fat mass, visceral fat volume, blood lipid levels, fasting plasma glucose levels, and glycated hemoglobin concentrations.
There were “no significant differences” in any of the outcomes between individuals of blood type A, individuals of blood type O, and any of the other participants. While, on average, all the participants lost weight, researchers concluded that blood type is not associated with the effects of any kind of specified diet.
One of the study’s authors noted that plant-based diets “turned out to be beneficial for people of all blood types, and there was no evidence that meaty diets are good for anyone.”
The keto diet
You may have heard of the ketogenic diet, which aims to keep the body in a state of ketosis, burning stored fat for fuel rather than glucose from carbohydrates. According to Harvard Health, the diet involves consuming fewer than 20-50 g of carbs per day, instead aiming to get as much as 90% of calories from fats. According to Harvard Health, this means many unhealthy saturated fats (like oils, lard, and butter) are encouraged for the diet, while fruits and vegetables (which contain carbohydrates) are restricted to small portions.
It may help you lose weight, but the keto diet brings numerous risks. Those on the keto diet are likely to increase LDL cholesterol levels, which raise the risk of heart disease. It can also lead to deficiencies in various nutrients, including selenium, magnesium, phosphorus, and vitamins B and C. Additionally, the diet could lead to liver problems, kidney problems, constipation, and mood swings.
In short, while some evidence suggests that this diet can lead to short-term weight loss, it remains unclear whether the keto diet is safe, or whether it works for long-term weight loss.
Click here to learn more about the keto diet on MDLinx.
The raw food diet
When US News and World Report released its ranking of the best (and worst) diets to try in 2021, the raw food diet came in at number 32 of 39. A panel of nationally recognized nutrition and health experts compiled the ranking, judging the diets based on nutritional value, impact on short-term and long-term weight loss, effect on heart health, and various other categories. They gave the diet a rating of 2.2 out of 5, concluding that scientific evidence to support the claims around the diet’s efficacy is lacking.
The diet is relatively simple: You can only eat foods that haven’t been processed or cooked. Roughly 75%-80% of the diet is plant-based, but some raw foodists will consume raw animal products, like unpasteurized milk, raw cheeses, sashimi, and certain raw meats.
Unfortunately, most of those who follow this diet consume half of their recommended daily caloric intake. This can lead to nutritional deficiencies, including a lack of calcium, vitamin B-12, and vitamin D.
When it comes to safety, the panel reported that the raw food diet ranks among the most dangerous. This is partially because of the risk of food poisoning, which can stem from consuming certain raw fruits and vegetables, including kidney beans, sprouts, buckwheat, and cassava.
The carnivore diet
According to a medically reviewed article published by Diet Doctor, the carnivore diet is exactly what it sounds like: A plant-free diet that involves eating only animal products.
The diet is almost universally not recommended. In blunt terms, registered dietician Amy Gorin, RDN, told Everyday Health, “This is not a healthy or sustainable diet.”
Gorin cited the diet’s high levels of saturated fat, which can raise LDL cholesterol and increase risks of heart disease, and its lack of fruit and vegetables, which are “known to promote weight loss and help fight disease.”
Similarly, according to Harvard Health, numerous studies have found that consuming large quantities of red and processed meats can increase risks of cancer, diabetes, and premature death.
The food-combining diet
While perhaps the least mainstream of the diets on this list, the food-combining diet is roughly a century old. According to a medically reviewed article published on Very Well Fit, the idea is that eating certain foods together and other foods separately can help enhance digestion and support weight loss. While there are different variations, here’s an example of one of its rules: Protein and grains can be eaten together, while protein and starch cannot.
The biggest problem is that there’s no scientific evidence that supports these ideas. Registered dietician Willow Jarosh, RD, points out that a common version of the diet forbids the consumption of protein and carbohydrates together.
“Many health experts suggest eating protein with carbohydrates to stabilize blood sugar and provide satiation,” Jarosh said.
Beyond that, the diet is notoriously hard to follow, may be unsafe for certain populations (like those with diabetes, who shouldn't consume carbohydrates alone), and is unlikely to lead to long-term weight-loss.
All of that said, maybe you’re ready to chuck the idea of a trendy diet, and just try eating healthier? Check out These 7 habits are sabotaging your diet on MDLinx.