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Experts say a change in lifestyle is probably more effective than any specific diet. Getty Images

Every year, millions of people turn to the internet to research the latest diet trends.

Google has released its top trending diets of 2019 and while experts say some of them may be helpful, others are not worth the effort.

Here’s how the experts weighed in on five of the top diet searches for this past year.

As the name implies, this diet limits intake to 1,200 calories a day.

The Dietary Guidelines for the United States recommend a calorie intake of between 1,600 to 2,400 each day for adult women and 2,000 to 3,000 calories every day for men.

Lauri Y. Wright, PhD, an assistant professor in public health at the University of North Florida, says for those wanting to lose weight, cutting calories is important.

“Creating a calorie deficit is the key to losing weight. The body then draws on stored fat for the necessary energy needed by the body, which is seen as weight loss,” she told Healthline. “We caution about diets that are too restrictive because very low calorie diets can slow your metabolism permanently. Too low is generally thought of as below 1,200 calories for women and 1,500 calories for men.”

It’s important that those restricting calories still achieve their nutrient needs.

“The diet needs to include all the essential nutrients for health,” Wright said. “The lower the calories, the tougher it can be to get all the protein, vitamins, and minerals necessary. We always recommend working with a registered dietitian that can plan the most healthful eating plans to meet your health goals.”

Dana Hunnes, PhD, a senior dietitian at the University of California Los Angeles Medical Center, says unless a person has low calorie needs or is under the direct guidance of a medical professional, cutting calories to 1,200 a day is not sustainable in the long term.

“This would definitely be considered more of a crash diet as opposed to a long-term lifestyle solution and I do not recommend it,” she told Healthline. “It is better to lose weight gradually over time and in a manner that is sustainable over the life time… this is not that type of dietary plan and it is not enough. It would likely make your own metabolism slow down since it would not be enough calories.”

One of the top diet search terms for 2019 was intermittent fasting.

“In the most basic terms, there are two main versions; time restricted eating (TRE), which is eating during only an 8-hour or 10-hour period or a 5:2 approach where women eat only 500 calories split between two meals, two times a week. Men get 600,” said Kristin Kirkpatrick, a registered dietitian and manager of wellness nutrition services at the Cleveland Clinic Wellness Institute in Ohio.

“The benefits are expansive, including longer life, weight loss, and chronic disease risk reduction,” she told Healthline.

Hunnes says other possible positives to intermittent fasting include benefits to the gastro-intestinal system by giving it time to rest and lowering inflammation throughout the body.

But fasting isn’t appropriate for everyone.

“Intermittent fasting is not a good plan for pregnant women or those with certain health conditions such as diabetes,” Wright said. “Additionally, one study found that intermittent fasting can harm heart health. Additionally, after losing weight with intermittent fasting, the body may gain back the weight more quickly because the body viewed fasting as starvation.”

Earlier this year, singer Jennifer Lopez announced she was attempting a 10-day challenge of no carbohydrates and no sugar.

Days into her diet, Lopez encouraged her followers to join her.

However, experts say some carbs are necessary.

“Our brains depend on glucose derived from carbohydrates for healthy functioning as do our muscles,” said Hunnes. “This type of diet is not healthy. Of course, limiting or avoiding sugar is healthy, but limiting all carbohydrates is not.”

Wright agrees.

“Carbohydrates are critical for health. However, the problem for many people is the type and amount of carbohydrates consumed. Emphasizing complex carbohydrates such as whole grain pastas, rice, beans, vegetables, and fruit rather than simple sugars such as soda and candy is crucial,” she said.

“Besides energy to fuel the body, carbohydrates also provide important vitamins, minerals, and fiber,” Wright added. “Carbohydrates are essential and should not be eliminated from the diet. Rather, choose healthy carbohydrates and control the portions. Excessive carbohydrates can add unwanted calories and cause high blood sugars for diabetics.”

Wright suggests an appropriate carbohydrate portion would be half to one cup of pasta rather than an entire plate or one-third to two-thirds of a cup of rice rather than a whole bowl.

Last year, the high fat, low carb keto diet topped Google’s trending diet searches.

This year, a variation of the diet called “keto ultra,” which includes supplements, made the top 10 most searched diets.

“The ketogenic diet is very low in carbohydrates and very high in fat, putting the body into ketosis — the burning of fat instead of glucose for fuel,” Wright said. “The keto diet has been shown to reduce weight because with any diet that restricts entire food groups, it’s possible that reduced dietary variety leads to reduced calorie intake. A side effect of ketosis is decreased hunger, which also contributes to weight loss.”

But the diet comes with risks.

“Because carbohydrate-containing foods such as fruits, vegetables, whole grains, and beans are eliminated, a ketogenic diet can contribute to certain vitamin and mineral deficiencies and may negatively impact gut health,” Wright said. “People following a ketogenic diet have also been shown to lose muscle mass, which is especially problematic for older adults.”

Hunnes argues a keto-based diet is not healthy.

“I do not think this is a healthy choice since evolutionarily speaking, we thrive on glucose as our major energy source. A high-fat, high-protein diet is not healthy for us at all. I, in as strong of terms as possible, do not recommend a ketogenic diet,” she said.

Both Wright and Hunnes note that the only people who could truly benefit from a keto-based diet are children who experience seizures and follow the diet under medical recommendations from their doctor.

“The ketogenic diet has been shown to successfully treat severe epilepsy in infants and children under medical supervision,” Wright said.

A diet popularized for its inclusion of dark chocolate and red wine was highly searched for in 2019.

The creators behind the sirtfood diet argue that “sirtfoods” can prevent disease and result in fat loss by activating a “skinny gene.”

“The sirtfood diet includes foods that contain seven proteins shown to decrease inflammation. Sirtfoods include red wine, dark chocolate, kale, berries, and soy,” Wright said.

Some of the other sirtfoods encouraged in this diet include strawberries, onions, blueberries, walnuts, coffee, and medjool dates.

But although the creators of the diet say eating such foods will activate a skinny gene, experts say there is no proof to back the claims.

“There is no evidence that the sirtfoods can turn on a skinny gene. The anti-inflammatory foods combined with calorie restrictions are more of the factors contributing to weight loss,” Wright said.

Hunnes agrees.

“Anything that sounds too good to be true often is,” she said.

As 2019 draws to a close and people begin making goals and resolutions for the new year, all of the experts who spoke with Healthline advise focusing on making sustainable lifestyle changes, rather than following extreme diets.

“Start before New Year’s. Don’t make that date an artificial time to start good habits and be aware that the best diet for you is the diet that you can stay on long term,” Kirkpatrick said.

“Get away from the term diet and think of a lifestyle change that will support sustained success,” Wright said. “Look at making small changes that will add up to a big impact. Look to something like the Mediterranean diet plan that is plant-forward with vegetables, fruit, whole grains, and lean fish and meats, and uses healthful fats. Combined with activity, this is a plan that you can live with and achieve your health goals.”