While the highly popular keto diet seems to be part of many people’s New Year’s resolutions, not everyone is a fan -- including celebrity trainer Jillian Michaels.

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In an interview with Women's Health magazine, Michaels, 44, criticized the low carb, high fat diet.

“I don’t understand. Like, why would anybody think this is a good idea?” Michaels said in a video.

Adherents to the keto -- short for "ketogenic" -- diet usually eat less than 50 grams of carbohydrates per day, according to the Mayo Clinic. People on the diet get most of their calories from fat. Instead of burning carbs for energy, the body burns fat, entering a state called ketosis.

The diet has taken off, with celebrities like Kourtney Kardashian and Halle Berry singing its praises, according to People Magazine.

The keto diet may result in weight loss for some who try it, but Michaels said it can deprive your body of essential nutrients. She cited the three macronutrients needed by humans: protein, fat and carbohydrates.

“When you do not eat one of the three macronutrients -- those three things I just mentioned -- you’re starving your cells,” Michaels said. “To make a very long story short, avoid the keto diet.”

Instead, Michaels recommends “exercising, limiting your processed sugars and grains, and keeping an eye on your calories,” Women’s Health reported.