Does counting calories help you lose weight?
For a long time, shedding pounds was considered a simple matter of accounting: if calories consumed exceed energy expended, then the balance is stored as fat. But does the old calorie-counting theory still add up? Sue Quinn does her sums.
A new way of thinking is gathering momentum. According to some scientists and nutrition experts, there’s more to losing and gaining weight – and staying healthy – than simple numbers. Emerging evidence suggests not all calories are created equal as far as our metabolism is concerned. In other words, certain foods are more likely to cause weight gain than others, even if they contain the same number of calories.
What’s more, some experts in the treatment of obesity now believe that calorie-counting is an outdated approach that doesn’t work and overshadows the importance of good nutrition. They point to the growing obesity crisis and rise in weight-related health problems that have occurred while calorie-counting has been the cornerstone of official weight management advice.
What exactly are calories?
The human body needs energy for breathing and organ function right through to working out at the gym. This energy comes from food and drink and is measured in calories. (Confusingly, what we think of as calories are officially known as kilocalories, or kcals, and this is how they appear on food labels.)
The system of measuring food energy in calories was devised in the late 19th century by American nutritionist Wilbur Olin Atwater. He worked out the calorie content of different foods by burning them in a sealed container and measuring the heat released. It emerged that one gram of fat contains around nine calories, while a gram of protein and carbohydrate each contain around four calories. Alcohol contains around seven calories per gram.
Today, the NHS advises that men need around 2,500 calories per day and women around 2,000 to maintain a healthy body weight and recommends reducing this intake to slim down. The NHS website does point out that the calorie system is not completely accurate. For example, it explains that it doesn’t account for the fact that bodies metabolise some foods more efficiently than others. More energy is needed to digest raw and whole foods than processed foods of the same calorific value.
The nutrient conundrum
Another problem with calorie counting is that it doesn’t prioritise nutrient-rich foods. For this reason, the British Nutrition Foundation (BNF) recently came up with its Quality Calorie (QC) concept to encourage people to consider the nutrients, not just the number of calories, in their food. For example, it suggests opting for wholegrain toast with peanut butter rather than white toast with butter and jam. Both contain roughly the same number of calories, but the first option contains more fibre, iron and protein and less free (added) sugar.
“If we only think about how many calories we’re eating and drinking, we might choose to avoid foods that are higher in calories but have high nutritional value, such as nuts and seeds, oily fish and olive or rapeseed oil,” says BNF nutrition scientist Sarah Coe.
Recent research has highlighted other potential problems with focusing solely on calorie counts. A major study published in British Nutrition Foundation (formerly the British Medical Journal) in November 2018 identified that calories from different sources are metabolised in different ways. Researchers fed 164 adults all their meals and snacks for 20 weeks and found that those on a low-carb/high-fat diet burned roughly 250 calories more per day than people who ate a high-carb/low-fat diet. In other words, they speeded up their metabolism (the complex system that turns food into energy) by getting their calories from sources other than carbs.
…And more evidence
Another study published in the journal Obesity Reviews in September 2018 found that sugar-sweetened drinks were worse for weight gain and chronic health problems than calorie-equivalent amounts of starchy foods such as potatoes.
“Calories from any food have the potential to increase the risk of obesity and cardiometabolic disease because all calories can directly contribute to positive energy balance and fat gain,” the study concluded. “However, various dietary components or patterns may promote obesity and cardiometabolic disease by additional mechanisms.” In other words, it’s complex.
Sarah Coe argues there is still no robust evidence that low-carb diets are the most effective for long-term slimming, and that calorie-counting needs to play a part. “Controlling calorie intake, using appropriate portion sizes and ensuring nutrient recommendations are met are all still essential to support weight management and good health,” she says.
But if counting calories sits at the heart of official weight management advice, why is obesity still a growing problem?
Dr Stuart Flint, a psychologist specialising in obesity and public health at Leeds Beckett University, says the causes of obesity are complex and generally can’t be addressed by calorie-controlled diets. Factors such as genetics, gut health, mental health and levels of physical activity all contribute.
''Low-calorie diets fail in the long term...after a few years, some people gain more weight than they lost''
Low-calorie diets fail in the long term. Research shows that, after a few years, some people gain more weight than they lost. Evidence suggests this is because when you take in fewer calories your metabolism slows down to prevent more weight loss. “We should focus on behaviour (like food choices and physical activity) to lead to longer-term change,” says Dr Flint.
He wants to see official health advice shift away from its focus on weight loss towards educating the public about how to make nutritious food choices. “You can stick within the calorie guidelines, but actually your diet might be extremely unhealthy,” says Dr Flint.
The bottom line
Research suggests that weight management is far more complex than balancing calories in and calories out. Not all calories are metabolised in the same way, and the causes of being overweight can’t be tackled through diet alone. Nutritionists and obesity experts do agree that managing weight and staying healthy require more than just controlling the number of calories consumed. The quality of the nutrients in those calories is equally, if not more, important.