Truth behind trending diets exposed

19th July 2021 | Clare Collins, Lee Ashton & Rebecca Williams

Diets claiming you’ll lose a huge amount of weight in next to no time pop up on social media relentlessly. When a new diet promises dramatic results with little effort, or sells miraculous pills, potions or supplements guaranteed to melt body fat or speed a up sluggish metabolism – with testimonials touting success – then be sceptical. We evaluated four current diet trends to see how their claims stack up against the science.

Reverse dieting might be a big hit with Insta influencers, but its weight-loss effects aren’t supported by science.

Reverse dieting

Reverse dieting, referred to as “the diet after the diet”, involves increasing your energy intake in a gradual, step-wise way after you stop following a reduced energy diet. The reverse diet is popular among bodybuilders and physique athletes trying to return to “normal” eating patterns without gaining extra weight. The theory is that providing a small energy intake surplus may help restore circulating hormone levels and reverse any adverse change in the body’s energy expenditure, restoring it to pre-diet levels.

At the same time, it tries to match energy intake to a person’s usual metabolic rate, based on them being at a stable weight. The aim is to try not to store any extra body fat while you’re consuming more calories than are being burned.

Anecdotal reports of success using reverse dieting have seen it trending, but there are no studies specifically testing this diet for weight management. Ideally, weight-loss strategies should maximise any reduction in body fat stores while conserving or building muscle mass. One review evaluated studies estimating the number of extra calories needed daily to maximise muscles and minimise body fat stores, while also exercising to build muscles (AKA resistance training). They found limited evidence to guide recommendations.


The first stages of the GAPS diet involve a lot of broth. And not much else.

The GAPS diet

The Gut and Psychology Syndrome (GAPS) diet starts with a strict elimination diet followed by maintenance and reintroduction phases that proponents suggest you follow over several years. There is no scientific evidence to support the website claim that the diet could lift a “toxic fog off the brain to allow it to develop and function properly”.

The GAPS diet wasn’t specifically formulated for weight management; rather, it’s promoted as a natural treatment for people with digestive problems or conditions that affect the brain, such as autism. But the website reports that some people have experienced positive weight changes, either weight loss or weight gain, as needed.

The diet recommends removing all grains, pasteurised dairy, starchy vegetables and refined carbs and swapping these for fish, eggs, broths, stews and fermented foods. The GAPS protocol also recommends a range of supplements including probiotics, essential fatty acids, digestive enzymes and cod liver oil… which happen to be for sale on the website.

Anyone for an enema?

The GAPS diet says that increased intestinal permeability, or “holes in your gut” (better known as leaky gut), allow food components and bacteria to enter your blood, which it says then triggers neurological and psychological conditions including depression, autism and learning difficulties. GAPS claims to heal a leaky gut by eliminating certain foods that trigger it, improving digestive and psychological health in the process.

While intestinal permeability is increased in some situations including pregnancy, during endurance exercise or with the use of non-steroidal anti-inflammatory medication (eg, aspirin and ibuprofen), there’s no evidence the GAPS diet regime resolves this.

Further, any bouts of diarrhoea experienced while following the GAPS diet are not “clearing you out”. There is no scientific evidence that diarrhoea caused by this diet is helpful, or a “natural cleansing reaction” to move toxins out of your body. Ultimately, the GAPS diet is extremely restrictive and puts you at risk of malnutrition. We strongly advise against it.


HCG for weight loss hasn’t been approved by the Therapeutic Goods Administration.

The HCG diet

Human chorionic gonadotropin (HCG) is a hormone produced during pregnancy (pregnancy tests check for HCG levels) and used in fertility treatments. HCG supplementation has also been used in athletes because it promotes testosterone production and builds muscle in males. It’s currently on the World Anti-Doping list of prohibited substances.

HCG is promoted as a weight-loss supplement, with older claims it could mobilise fat and suppress appetite. The original 1954 HCG trial which was published in medical journal The Lancet had some positive results and triggered development of the current HCG diet.

The diet involves taking an HCG supplement, typically as liquid drops, while following a very low-energy diet of a punishing 500 calories (2000 kilojoules) a day. Since 1954, no studies have replicated the original findings. The conclusion? Any weight loss is due to the large energy deficit. We don’t recommend this diet.


IIFYM focuses too much on macronutrients and not enough on vital micronutrients.

IIFYM (If It Fits Your Macros) diet

Instead of counting calories, the IIFYM diet gets you to count your macronutrients (macros). First you use their online calculator and fill in a range of questions related to your plans to manage your weight. You supply your email and it works out your daily macro needs and sends you a copy, plus an “offer” for a personalised program with a money-back guarantee.

You then monitor your daily intake of protein, carbohydrates and fat in grams coming from food and drinks (although you can count macros on any app). Depending on a person’s individual goals, the diet may or may not include a daily calorie restriction.

There is no research specifically testing the IIFYM diet. But lots of research has tested whether certain macro ratios are better for weight management. The short answer is no.

A review of 14 popular diets with varying macronutrient ratios that was published in the British Medical Journal found no specific diet was better than others in achieving weight loss over six months. Across all diets, weight loss diminished by 12 months.

For weight loss, the key to success is achieving a daily calorie restriction you can live with. Focus on which foods your macros are coming from, rather than the ratio. By eating foods of higher nutritional quality – like vegies, fruit, legumes and whole grains – rather than energy-dense, nutrient-poor ultra-processed foods, your total calorie intake will be lower.

Counting macros can inform food choices that boost diet quality and help lower calorie intake, but there’s no strong evidence behind this diet.


For personalised help to check whether you’re meeting your nutritional requirements, consult an Accredited Practising Dietitian. Due to COVID-19, Medicare has introduced rebated telehealth consultations for eligible people.

This article was written by Clare Collins, Professor in Nutrition and Dietetics, University of Newcastle; Lee Ashton, postdoctoral research fellow, University of Newcastle; and Rebecca Williams, postdoctoral researcher, University of Newcastle. The article was originally published by The Conversation and has been edited for style and clarity.