Low-carbohydrate diets can help some adults manage their weight, but cutting carbohydrates is not necessary for a healthy diet, and the quality of the foods being eaten matters more than simply reducing carbohydrates.
The World Health Organization says carbohydrates are the body’s primary source of energy and recommends that, for most people, they should make up a significant part of the diet. It recommends getting carbohydrates mainly from whole grains, vegetables, fruits and pulses such as beans and lentils.
This is an important distinction because not all carbohydrates have the same nutritional value. Foods such as whole grains, fruits, vegetables and legumes provide carbohydrates along with fibre, vitamins and minerals. Free sugars, highly processed foods and sugary drinks are different and should be limited as part of a healthy diet.
What low-carb diets involve
There is no single definition of a low-carbohydrate diet. Some eating plans substantially reduce foods such as bread, rice, pasta and other carbohydrate-rich foods, while allowing greater amounts of protein and fat.
The evidence suggests that low-carbohydrate diets can help with weight loss for some people. However, research does not show that simply reducing carbohydrates makes one diet universally better than another in the long term. Harvard’s review of the evidence notes that healthy diets with different proportions of carbohydrates, protein and fat can produce similar long-term results.
For that reason, the focus should not be on eliminating carbohydrates altogether. A sustainable eating pattern should provide adequate nutrients and include a variety of foods.
Choosing healthier sources of fat and protein
When carbohydrates are reduced, what replaces them matters.
The WHO recommends favouring unsaturated fats, which are found in foods such as fish, avocado and nuts and in oils such as sunflower, soybean, canola and olive oil. Saturated and industrially produced trans fats should be limited.
Protein can come from a range of foods, including fish, poultry, eggs, beans, peas, lentils, nuts and seeds. A healthy diet does not require people to rely only on meat and eggs.
What about weight loss?
Weight management depends on several factors, including overall food intake, physical activity and whether an eating pattern can be maintained over time. The NIDDK says successful weight-management plans generally involve a healthy eating pattern that can be followed over the long term rather than a short-term restrictive diet.
Some studies have found advantages for low-carbohydrate diets, particularly over shorter periods. But the longer-term evidence does not establish low-carbohydrate eating as a universally superior approach. The quality of the foods and the overall nutritional balance remain important.
A balanced approach
Healthy eating does not mean avoiding bread, rice, potatoes, fruit or other carbohydrate-containing foods altogether.
WHO guidance recommends a varied diet built around minimally processed foods, with carbohydrates coming mainly from whole grains, vegetables, fruits and pulses. It also recommends limiting free sugars, salt, saturated fats and industrial trans fats.
For people considering a major change to their diet, especially those with a medical condition or particular nutritional needs, advice from a qualified health professional can help ensure that the eating pattern provides adequate energy and nutrients.
The evidence therefore supports a more measured view of low-carbohydrate diets: they can be one option for some adults, but a healthy diet does not require carbohydrates to be eliminated, and reducing carbohydrates alone does not guarantee better health.
