The low-carb, high-fat regime is still wildly popular — but new research reveals both the mechanisms behind its success and the risks it carries

 Once a fringe eating plan favoured by biohackers and weightlifters, the keto diet has morphed into a mainstream nutritional movement. But what’s behind its staying power — and are there real benefits, or is it just another well-packaged fad?

In a new episode of Science Weekly, host Madeleine Finlay dives into the ketogenic diet with Professor Javier Gonzalez, a specialist in personal nutrition at the University of Bath. Together, they unpack the latest research on how keto works, its potential impacts, and the science behind the sometimes dramatic results.

What is the keto diet, really?

At its core, the ketogenic diet is a very low-carbohydrate, high-fat eating plan that shifts the body’s metabolism. By cutting carbs to roughly 20–50g per day, the body enters ketosis — a state where it burns fat for energy, producing ketone bodies as a byproduct.

Professor Gonzalez explains: “Your body essentially thinks it’s starving — but instead of using glucose from carbohydrates, it flips to burning stored fat.”

Why does it help people lose weight?

The weight loss effect, Gonzalez notes, is multifaceted. Initially, much of it comes from water loss — as stored carbohydrates (glycogen) are depleted, water is released. But over time, the diet tends to naturally reduce calorie intake.

“Fat and protein are more satiating,” he says. “People simply eat less, even without consciously trying to restrict calories.”

There’s also evidence that ketone production may help suppress appetite directly, although the strength and consistency of this effect varies between individuals.

What are the risks?

While keto can offer quick results, there’s a catch. Gonzalez warns of several concerns, especially for those attempting the diet long-term:

• Nutrient deficiencies, due to limited intake of fruits, vegetables, and whole grains.
  
• Increased cholesterol and LDL in some individuals, due to the high intake of saturated fats.
  
• Gut health disruption, such as low fibre intake, may negatively affect the microbiome.
  

And there’s the issue of sustainability. “It’s very hard to maintain over months or years,” Gonzalez says. “And if someone comes off keto without adjusting habits, they’re likely to regain the weight — sometimes even more.”

Is keto good for everyone?

Short answer: no. While some people with type 2 diabetes or epilepsy may benefit medically, most people may not need such a strict approach.

“We need to move away from one-size-fits-all diet messaging,” Gonzalez adds. “The most important diet is one someone can sustain — physically, mentally, and socially.”

The verdict?

The ketogenic diet isn’t a magic bullet, but it’s also not pseudoscience. It works — just not always for the reasons people think. Much of the weight loss success comes from reduced calories and hunger, not necessarily the ketones themselves. And the restrictive nature of keto makes it hard to recommend as a lifelong plan for most.

Instead, Gonzalez and Finlay conclude, the key lies in understanding your own body — and choosing dietary strategies that prioritise health over hype.

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