Cutting out carbs: What does the science say about a low-carb diet?

Not long ago, a video went viral showing a waiter placing a pizza on a woman’s plate. She responded, “Do I look like I eat carbs?” Her tone made it seem as though he had done something inappropriate. While the moment may have been amusing—or even staged—it highlights a growing trend of cutting out carbs and a broader shift towards the low-carb diet.

Research suggests that around 3 million people in the UK have tried low-carb diets. Yet the NHS recommends that starchy carbohydrates should make up about a third of our diet. So why are people cutting them out?

What is driving the decline in carbohydrate intake?

This trend has led to the term carbophobia. Although not a formal scientific or medical term, people use it to describe an excessive fear of carbohydrates based on the belief that they are inherently bad or unnecessary. This mindset often underpins the growing popularity of the low carb diet.

Large-scale dietary surveys and systematic reviews provide strong evidence for this shift. For example, one review covering 47 countries over 70 years found that carbohydrate intake has steadily declined in many Western countries since the 1960s. As a result, people increasingly avoid staple foods such as whole grains, rice, legumes, fruit, oats, and even some vegetables simply because they contain carbohydrates.

This reduction has important consequences—not just for general health, but also for athletic performance.

Why are people cutting out carbs?

Although most research focuses on what people eat rather than why they choose specific nutrients, several factors appear to drive the decline in carbohydrate consumption:

• The growing popularity of low-carb and ketogenic diets
• Weight-loss messaging that demonises carbohydrates
• The rise of high-protein, high-fat diet trends
• Misunderstandings about insulin and fat storage
• Confusion between refined carbohydrates and healthier sources
• The influence of social media fitness personalities
• Misinterpretation of scientific research
• Fear of blood sugar spikes

Ultimately, many people view carbohydrates as unhealthy—or even unnecessary—due to myths and misunderstandings. For instance, some believe that bodybuilders eat high-protein diets with little to no carbohydrate. In reality, while they may reduce carbs before competition, carbohydrates remain a key part of their diet. Eight-time Mr Olympia winner Ronnie Coleman reportedly consumed around 500 grams of carbohydrates per day, while four-time winner Jay Cutler consumed between 400 and 1,000 grams daily.

Why carbohydrates are a key part of a balanced diet

Like other phobias, carbophobia stems from misconceptions rather than evidence. Education plays a crucial role in addressing it.

To shift attitudes, we should replace myths with clear, relatable explanations grounded in physiology and performance. Avoid framing foods as “good” or “bad.” Instead, focus on how the body actually works and provide practical examples people can apply.

Carbohydrates are fuel: the body’s primary energy source

People respond well when we explain that carbohydrates serve as the body’s primary energy source. They fuel everything from brain function and red blood cells to high-intensity exercise.

Glycogen—the stored form of carbohydrate—plays a vital role, but the body stores only a limited amount. These stores deplete quickly. For example, performing just six sets of 12 leg extensions can reduce glycogen in the quadriceps by nearly 40%. As glycogen levels fall, the body struggles to maintain exercise intensity, work output drops, and tissue breakdown increases.

Whether someone performs endurance exercise, high-intensity intervals, or resistance training, glucose provides the main source of energy.

The brain also relies heavily on glucose. As a result, very low-carbohydrate diets often lead to irritability, poor concentration, and low mood.

How carbohydrates support muscle growth and recovery

Many people accept that carbohydrates fuel exercise, but fewer recognise their role in building muscle. In reality, carbohydrates support the entire process.

They provide the energy needed for intense training, reduce muscle breakdown, and accelerate recovery by replenishing glycogen stores. They also support nervous system function and help create an anabolic environment.

When carbohydrate intake is too low, the body compensates by breaking down protein and increasing stress hormones such as cortisol. This response can negatively affect both immunity and muscle mass.

Importantly, diets do not need to eliminate carbohydrates entirely to cause these effects. Research shows that diets with 35% or less carbohydrate can lower testosterone levels while increasing cortisol. For this reason, experts recommend carbohydrate intakes of at least 3–5 g/kg/day to support muscle growth—significantly higher than protein recommendations of 1.4–2.0 g/kg/day.

Not all carbohydrates are created equal

Rather than arguing about whether carbs are “good” or “bad,” shift the conversation towards understanding different types of carbohydrates.

Blaming carbohydrates for conditions like obesity or diabetes oversimplifies a complex issue—much like blaming fat for heart disease or protein for kidney problems.

A more useful approach highlights that the issue lies not with carbohydrates themselves, but with highly processed, low-nutrient foods. In contrast, whole, nutrient-dense carbohydrate sources provide fibre, vitamins, minerals, and phytonutrients that support energy metabolism, gut health, and cardiovascular function.

This distinction helps people separate carbohydrates as a macronutrient from less healthy food choices.

Turning advice into practical food choices

Telling people to “eat more carbohydrates” is not helpful unless they know how to do it.
Offer simple, practical examples of balanced meals that include healthy carbohydrate sources:

• Oats with fruit and yoghurt
• Rice or potatoes with lean protein and vegetables
• Wholegrain wraps with beans, lentils, or quinoa

Why carbohydrate needs aren’t one-size-fits-all

People respond better to advice that acknowledges nuance rather than taking an all-or-nothing approach.

While most healthy individuals benefit from adequate carbohydrate intake, some people do well on lower-carbohydrate diets. Certain conditions, such as diabetes, may also require more careful carbohydrate management.

Physical activity levels also influence carbohydrate needs. For example, 3–5 g/kg/day supports muscle growth, while endurance athletes may require 6–10 g/kg/day.

Carbohydrate needs can also change over time. A bodybuilder may reduce carbohydrate intake before a competition to lower body fat, then increase it shortly before competing to maximise muscle fullness. Endurance athletes similarly increase carbohydrate intake before events to maximise available energy.

Recognising these differences makes recommendations more credible and more useful.

Reframing the conversation around carbohydrates

Carbophobia describes a growing fear of carbohydrates, often driven by trends such as cutting out carbs or following a low-carb diet based on the mistaken belief that they are harmful or unnecessary. This fear stems from misinterpreted science, social media influence, and confusion between refined and whole-food carbohydrate sources.

We can address this trend by replacing myths with clear, evidence-based explanations rooted in physiology, performance, and practical guidance. When people understand the role and benefits of healthy carbohydrates, their fear is likely to diminish.

For those who want to explore this topic in more depth and learn how to apply these principles in practice, our nutrition courses provides a more comprehensive breakdown of macronutrients, dietary strategies, and real-world coaching approaches.

Author

Paul Orridge

Paul Orridge BSc (Hons)

Paul Orridge is a graduate in the field of sport, exercise and health, and has over 30 years’ experience within the fitness industry. In this time, he has performed a variety of roles including personal training, lecturing and writing. Paul now works as a freelance technical author and subject matter expert within the fitness industry. His work is based on his practical experience gained working with a diverse range of people from very unfit, overweight individuals to highly conditioned athletes, and is underpinned by the latest research.