Extreme diets have long been a part of diet culture as quick-fix weight-loss solutions.
When I was growing up, these diets were found in women’s magazines and often called “fads” as they cycled in and out of fashion.
The grapefruit diet, cabbage soup diet, Atkins diet and more came and went.
But today, extreme diets have become more than just a way to quickly shed kilos. Diet devotees are looking to combat chronic health problems and “optimise” their health.
Examples of such diets in the modern day include carnivore, where you exclusively (or almost exclusively) eat meat, and keto, where you eat very low amounts of carbs and very high amounts of fat.
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Then there are mono-diets, where people eat a single food to the exclusion of all others — think a “potatoes-only” or “apples-only” diet.
Some of these extreme diets don’t seem to be cycling away, like the fad diets of old. They often have rules for eating that connect to a person’s belief systems or personal values — even give them a sense of social connection and belonging.
And they’re usually a far cry from the official recommendations on how we should eat, such as the Australian Guide to Healthy Eating.
But contrary to expectations, people on strict diets often report feeling better. They commonly mention less brain fog, more energy, improved sleep and better skin health. So what’s going on?
A ‘massive elimination diet’
I spoke to nutrition experts about the features of an extreme diet that could have people feeling better in the short-term for Radio National’s podcast Cooked.
The chief idea they raised was that such diets — where someone cuts out most typical food groups — could act as a form of elimination diet.
Elimination diets are used in medicine to figure out which foods people are having adverse reactions to. People cut their diet right back, removing dairy, gluten and more.
“You’ve eliminated potential allergens from your diet in the form of fruits, vegetables, grains, legumes, all of these different things,” says Richie Kirwan, a lecturer in nutrition from Liverpool John Moores University.
“People immediately feel better because all of these are gone from their diet.“
Having symptoms like skin issues, gut issues or fatigue are common reasons people look to extreme diets.
If these are caused by a reaction to certain foods, it would make sense that people feel better if they cut out those foods.
But the problem with extreme diets, Dr Kirwan says, is there’s no reintroduction phase where foods are slowly added back in to identify which one is a trigger.
The risk of missing out on that step is that while you may feel a bit better in the short term, you’re unlikely to get vital nutrients and potentially do long-term damage to your health.
Diets connect communities
Some evidence also suggests positive feelings people experience on extreme diets are psychological rather than physical.
By identifying with a particular diet, you join a community of like-minded folks who are in it together and often connect via online platforms or social media groups to provide encouragement and feedback.
People connect through food and diets. (Getty Images: Atstock productions)
This reinforcement is extraordinarily powerful, Janet Chrzan, a nutritional anthropologist at the University of Pennsylvania, says.
“It’s not just a reinforcement about your aims and your goals, or maybe allaying your fears, it’s also a social reinforcement because somebody is approving of what you’re doing.
“That is the core of what makes us happy as humans.”
Consider too the burden of decision making. On any given day, humans make an estimated 300 decisions about food.
Having strict diet rules with a restricted number of foods allowed simply cuts down those choices.
“The more options people have for what to eat, the more mental effort you have to make, and the more potential anxiety,” Dr Chrzan says.
Long-term impact of dieting
While feeling better in the short term is great, there are biological changes in chronic diseases that can occur behind the scenes.
“You can feel absolutely amazing. But things can be going on in your body that may not show for another 20, 30, 40 years,” Dr Kirwan says.
“And that’s particularly the case with cardiovascular disease.”
This is important in the case of the carnivore and keto diets because they tend to include high amounts of saturated fat. That’s a key risk factor for heart disease.
Restrictive diets can, in some cases, result in nutritional deficiencies that won’t be felt in the body and can only be picked up on testing.
So what should you do?
Be aware of the red flags around dieting. Be wary if someone is talking about a way of eating that involves strict rules, a quick fix or that excludes entire food groups.
While extreme diets can cause weight loss, people on such diets followed long term typically find them difficult to stick to after a few weeks and generally gain back the weight they have lost.
If you’re tempted to follow such a diet, stay in touch with your doctor so they can do regular check-ups and monitor your health.
Nutrition is a science full of nuance, and the devil is always in the details.
Dr Emma Beckett is a food and nutrition scientist and the presenter of the new Radio National series Cooked. Hear more about this topic and subscribe to the podcast for more evidenced-based information about diet and nutrition.