Nutritionists Warn Against This Popular Diet Trend Hurting Your Metabolism

Juicing Slows Down Metabolism

The juice diet or juice cleanse—where you get all your sustenance from juice—is not a good idea, for several reasons, but especially for weight loss. “When you’re swapping out food for juice, you end up not consuming adequate nutrition,” Amber Sommer, RD, LD, tells the Cleveland Clinic. “You’re not getting enough calories, protein or fiber. That can actually slow down your metabolism, which won’t help you lose weight. And it can have other negative effects, like brain fog, reduced energy levels and more. It’s not a safe way to approach weight loss.”

You Won’t Be Burning Fat

Doing a juice fast may result in you losing muscle mass rather than torching fat. “When you’re doing a juice cleanse, that initial weight loss is very likely to be from water weight,” Sommer says. “And over the long term, you’re likely to start losing muscle. To lose fat, you need protein. You need fiber. You need good, healthy carbs. None of which you get when you’re doing a juice cleanse. So, your body starts pulling energy from wherever it can.”

Removing Fiber

Fruit and vegetables contain important fiber that is removed by the juicing process. “When you make a smoothie, whatever goes into the blender comes out in your drink,” Natalie Romito, RD, LD, tells the Cleveland Clinic. “But with juicing, the pulp gets removed… Fiber is important for our bodies in a lot of ways. But when you’re juicing, you remove fiber from the food. That changes the way the natural sugars in that food work in your body. So, something like apple juice is much more likely to have a big effect on your blood sugar than eating a whole apple would.”

Blood Sugar Spikes

Removing the fiber leaves nothing but a ton of sugar, which is the enemy of weight loss. “Without fiber, sugar is more rapidly absorbed by your body,” Sommer says. “Fiber helps to slow your digestion and absorption of sugar. In turn, this helps keep blood sugar and hunger in check. When you eat fruit, your blood sugar doesn’t spike so much. When you drink fruit juice, it does. And that’s because you’re not getting the benefit of fiber to slow things down.”

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Juicing and Overconsumption

Juicing makes it easier to have more of something than intended. “Juicing makes it a lot easier to overconsume,” Romito says. “Most people will naturally moderate their fruit intake when they eat whole foods because they get tired of chewing it and the fruit’s fiber fills them up. You wind up taking in more sugars and more calories when you’re having a juice form versus when you’re having the whole food form. When you don’t have to chew food, you’re bypassing your body’s natural mechanisms that help regulate your eating.”

Nutrient Issues

The nutrients in juice are quick to deteriorate. “It is best to drink the juice right away, because antioxidant and enzyme activity decreases over time,” Mario G. Ferruzzi, a professor in the Department of Food, Bioprocessing and Nutrition Sciences at North Carolina State University tells CNN.

Metabolism Issues and Weight Gain

Unless you plan on drinking nothing but juice forever, going back to a regular diet will probably result in weight gain with some other unpleasant side effects. "More than likely, any weight that was lost will be regained shortly after solid foods are reintroduced, with the potential added downsides of a slower metabolism and bone loss,” wellness dietitian Amanda Beaver tells Houston Methodist.

Detox Claims

Approach any juice cleanse “detox” claims with caution. “The science of detoxifying is still being researched, so don't fall for the marketing ploys that juice cleansing companies are trying to sell you,” Beaver says. “Instead, focus on eating whole foods, including veggies, fruits, beans, nuts and whole grains. The fiber from these foods is thought to help eliminate some toxins, while their phytochemicals may help promote the detoxification of carcinogens."

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