Updated 13 December 2018

Here’s how going on fad diets can mess with your brain

So you've lost 10kg. But are you also losing your mind?

Keto, the Carnivore Diet and other restrictive diets are popular. That’s because they often work. People adopt the diet and they see results, sometimes dramatic, although often in the short term.

“Doesn’t he/she look great?” Is what you often hear. But my question, as a registered dietitian, is, “Yes, but how do they feel?”

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You see, restrictive diets – or diets that require you to eliminate foods or nutrient groups – can have negative effects on your brain.

Here are three I often see in my work with clients.

1. Increased cravings can turn obsessive.

Tell someone that they can’t have peanut butter on their diet (ahem, Paleo) and they’re more likely to crave peanut butter. Tell them they can only eat a few measly carbs daily (ahem, keto) and suddenly every deep-dish pizza, bowl-o-pasta, and loaf of bread looks even more delicious.

“It’s an inherent behaviour in people,” says Brierley Horton, a registered dietitian in Birmingham. “It’s like the kid who is told they can’t do or touch something and that’s all they want to do and then usually end up doing it. Tell me I can’t eat carbs and all of a sudden I see carbs everywhere and that’s all I am thinking about.”

Young dieting woman with hands tied with measureme

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Some people will tell you that cravings are your body’s way of telling you the nutrients it needs. Those people are wrong. No clinical research has ever shown this old nutrition chestnut to be true.

“The craving isn’t based on a need for nutrients, it stems from depriving yourself,” Horton says.

2. Cutting food groups deprives the brain of needed nutrients.

Take carbs again. Carbohydrates provide your brain with glucose, a fuel it needs to execute everything from basic to complex tasks. About a decade ago, when low-carb diets started gaining popularity, researchers studied the effects of a lack of carbohydrates on the moods of dieters. Sure enough, those study participants who ingested the few carbohydrates reported a poorer mood overall than those who ate a diet that included carbs.

Gluten intolerance concept. Young girl refuses to

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And it’s not just the brain that’s deprived. Carbohydrates aren’t just processed products like pizza and white bread. They include whole grains, vegetables and fruits. And if you’re not eating those foods, you’re missing out on fibre, antioxidants, and a host of other important vitamins and minerals that keep your entire body functioning and peak performance.

3. Closely monitoring nutrients may lead to disordered eating.

Research shows that restrictive or elimination diets may encourage disordered eating.

“Dieting is the number one risk factor for the development of an eating disorder,” says registered dietitian, Marci Evans, a certified eating disorder dietitian and supervisor.

In one study of women, those who followed a rigid diet (versus one deemed flexible) reported symptoms of an eating disorder and were concerned with their body size. The rigid dieters also typically had a higher BMI. I’ve seen this happen in men, too.

Mature woman female inspecting testing butter food

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There are some key signs that your eating has become problematic or disordered. “If your eating regimen ignores your body’s natural cues of hunger and fullness, creates more food obsession, and leaves you feeling guilty or ashamed, then it may be time to consider that your habits are causing more harm than good,” explains Evans.

That said, “not everyone who follows this type of diet will experience anxiety or guilt over food choices, but any time rules are created, you create a condition of ‘good or bad,’ ‘right or wrong’, which adds an emotional layer of complexity to our relationship with food,” adds Dr Kara Mohr. (She’s my wife, but also the co-owner of our nutrition consulting firm, Mohr Results.)

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The bottom line: I’m not saying that you should never try out the latest, hottest diet. It may even work for you. But if it’s not working for you mentally – even if it’s working for you physically – you may want to reassess.

This article was originally published on

Image credit: iStock 


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