Serving Up TikTok’s Viral 90-30-50 Diet Trend

Can you reduce well-being to a formula? The latest social media trend claims you can. Our experts aren’t convinced.

Another week, another viral wellness trend.

This time, a US influencer and dietitian claims to have unlocked the secret to weight loss and even autoimmune health.

The key? Adjusting your macronutrients according to a prescribed formula, and sticking to it.

Here’s why it might not work for you.

What is the 90-30-50 Diet Trend?

Popularised by TikTok dietitian Courtney Kassis, the 90-30-50 diet trend emphasises daily consumption of at least 90 grams of protein, 30 grams of fibre, and 50 grams of healthy fats. Kassis claims the diet helped her lose 15lbs and improve her autoimmune condition in just two months.

Unfortunately, the experts aren’t convinced.

“Of all the fads being generated on TikTok, here’s yet another one that is completely unfounded and possibly even dangerous,” says Alex Ruani, a UCL doctoral researcher in nutrition science education at The Health Sciences Academy.

Kassis, based in the United States, promotes the diet online and even sells a paid programme based on it. However, Ruani says there is no scientific evidence to support Kassis’s claims, and the diet’s formula is arbitrary.

“Dietitians are typically trusted professionals, which may explain why this trend has gained traction,” Ruani explains. “However, promoting a fad diet like this, without sufficient scientific evidence, undermines the credibility of the profession. In the UK we rarely see dietitians supporting questionable trends like the 90-30-50 diet, as it could be viewed as a breach of professional ethics.”

Ruani doesn’t hold back, warning that the claims around fat loss and disease remission may mislead the public and could potentially harm individuals who follow the advice without proper context. 

Dr. Indhira Ghyssaert, a registered nutritionist and GP at The Balance Healthcare Group, isn’t sold either.

“From my perspective, the popularity of specific health trends comes more from personality than from the actual science,” she says. “Many people sell different health tips and tricks exceptionally well, but that doesn’t mean it is a miracle solution to chronic diseases or weight loss.”

What Are the 90-30-50 Rules?

As the name implies, this diet sets rigid macronutrient targets of 90g protein, 30g fibre, and 50g fat per day.

The problem is, it doesn’t consider individual factors like age, body weight, activity level, or health conditions. Or, for that matter, your actual fitness goals. Bulking up? All that protein may be helpful. Training for your first half marathon? You might crave carbs instead.

“The rules are arbitrary and lack any scientific basis or rigorous testing,” says Ruani. “The 90-30-50 diet fails to account for potential adverse effects, nor does it caution followers that it could create more health problems than it solves,” she says. “Simply put, these combined ‘rules’ are completely made up.”

As for the science, well, there are currently no published studies or clinical trials to support this exact 90-30-50 formula for improving weight loss, health outcomes, or disease management.

“The claims of fat loss and even disease remission, as seen in the promotional content, are anecdotal at best and should not be presented as universal truths,” Ruani warns.

Does This Trend Make Sense, Nutritionally? 

In short, no.

Our protein requirements, for example, are typically calculated based on body weight (grams per kilogram), not a blanket figure like 90 grams.

For some, 90 grams may be too much; for others, it might be too little. Excessive protein consumption has even been linked to kidney strain in vulnerable populations and could lead to nutrient displacement, meaning other essential food groups are neglected.

“If you’re mostly inactive with a desk job and walk about 30 minutes a day, your daily protein needs likely range from 0.75 to 0.83 grams of protein per kilogram of your body weight, per the WHO guidelines,” Ruani says. “But, if for example, you’re recovering from an injury, your protein needs may increase by approximately 20-25% above the normal rate to repair the damaged tissue.”

It’s not all about total protein either. New research suggests that protein variety matters more. An 18-year-long observational study of 12,177 participants found that those who consumed protein from at least four different sources had a 66% reduced risk of high blood pressure compared to those who consumed fewer sources.

Both Ruani and Ghyssaert express concern that the type of fat in this diet isn’t specified. Followers might end up relying on harmful fats, such as trans fats found in pastries or peroxide-damaged fats from deep-frying.

“For a typical 2,000-calorie diet you would aim for around 70 grams of total fat and 20 grams of saturated fat, says Ruani. “The 50-gram target in the 90-30-50 diet is below this guideline and may be too restrictive for those with higher caloric needs.”

Is 90-30-50 Good for Weight Loss?

Without clinical testing, it’s difficult to say if this diet will help you shift weight.

The increased levels of protein and fibre may help promote satiety—the feeling of being full, which helps us not overeat —but Ruani thinks that the lack of focus on overall calories or sugar intake could mean some followers lose weight.

“It’s possible to hit the fibre target with breakfast cereals or sugar-loaded snack bars, or to consume all 50 grams of fat through butter or other calorie-dense sources,” she explains, adding that without thorough scientific analysis, the diet can’t be labelled inherently effective or reliable for weight loss.

Are There Any Upsides to It?

While our experts are sceptical of the trend, there may be some silver linings. After all, becoming more conscious of what you’re eating is rarely a bad thing, right?

If there’s a benefit to this diet, Ghyssaert points to its fibre content – a vital component of any diet, yet something most people don’t consume enough of.

“Fibre improves insulin sensitivity by slowing the digestion and absorption of carbs, which moderates blood glucose levels, reducing the risk of type 2 diabetes and aiding in weight management,” she says.

Fibre also lowers LDL (low-density lipoprotein) cholesterol, reducing the risk of atherosclerosis and cardiovascular disease. “It also helps us have regular bowel movements and prevents constipation,” adds Ghyssaert.

Moreover, fibre is an efficient, low-calorie way to fill up, which may explain Kassis’s weight-loss results.

But while adding more fibre is beneficial, Ruani cautions that doing so too quickly could cause digestive discomfort, bloating, gas, and even constipation.

Any Final Thoughts?

While Ghyssaert admits that some viral trends can be based around kernels of fact, she stresses that they should not be adopted blindly or completely, with each of us responding differently to different diets.

“It is a complex, personal process,” she says. “I always remind my patients that just because it works for someone else does not mean it will work for them.”