Can our bodies tell that sugary drinks are high in calories?

19 September 2018 | Healthy living

Sugary drinks are a hot topic at the moment, but what role do they play in weight gain, overweight and obesity? Susannah Brown, our former Head of Research Evidence and Interpretation at World Cancer Research Fund, explains some of the latest research and shares her tips for alternative thirst-quenchers.

Sugar and obesity. Two words found in many news stories in the UK this year. In January, the NHS announced that it was banning the sale of sugary drinks in hospitals. The UK-wide sugar tax on soft drinks came into effect in April. And in July and August came reports of a record high number of children with severe obesity and a ‘shocking’ rise in type 2 diabetes in children.

At World Cancer Research Fund, we know there’s a link between these things. Some soft drinks contain sugar, consuming too much sugar can cause us to become overweight or obese, and being overweight or obese is a known cause of 12 different types of cancer. Sugary drinks are often consumed alongside other unhealthy foods, and if you’re drinking sugary drinks at mealtimes, the total calorie content of the meal can rocket up. The energy content of sugary drinks is often described as empty calories – calories which don’t provide any additional nutritional benefit (in the form of other macro- or micronutrients) alongside the energy. Consuming more calories than we burn off knocks us out of energy balance and, over the long term, leads to weight gain, and unfortunately it’s much easier to consume calories than it is to exercise them off.

What happens when we drink sugar?

There’s actually some more complex mechanisms at play in our bodies when we drink sugary drinks, compared with when we eat sugary foods. Calories from food are more satiating – they make us feel fuller – than calories from liquids. If our bodies aren’t recognising these calories, it’s much easier to consume more than we need. 

This is known as lack of compensation: energy from sugars isn’t always registered by the body in the same way when consumed in a sugary drink as when consumed as part of a solid meal. It’s also been proposed that one element in sugary drinks – high fructose corn syrup – modifies how our bodies lay down fat. This key sweetening agent may promote the laying down of fat in the abdomen that surrounds important organs such as the pancreas and the liver, and increase fat and cholesterol in the blood, independently of an effect on body weight, although more research is needed to understand this process. High fructose corn syrup has largely been phased out in the UK, but consumption in other countries – notably Hungary and the US – is still high.

The good news is that sugary drinks are one of the easiest things to swap out of our diets. Everybody needs food to survive, but none of us have to drink sugary drinks. Drinking plain water can be a little bit boring so I often opt for sparkling water with a few cubes of pineapple or watermelon dropped in. Unsweetened tea and coffee are also great options.

The obesity crisis 

So, would cutting down on sugary drinks solve the obesity crisis and help bring down cancer rates? Well, obesity is a complex issue that requires all parts of government and society to work together to resolve it. At an individual level we recommend lots of additional ways to improve our diets, such as cutting down on high-calorie foods and avoiding alcohol (which people sometimes forget can be high in sugar). The most effective way of preventing cancer after not smoking is by adopting healthy patterns of diet and physical activity throughout life. 

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Susannah Brown | 19 September 2018