Tucking into a high protein meal washed down with a sugary drink may be a particularly unhealthy combination, research suggests.
A study in the journal BMC Nutrition found that consuming fizzy drinks together with foods such as meat and cheese can cause your body to store more fat.
It may also boost a craving for savoury and salty foods.
Priming the Body to Store Fat
Researchers from the US Department of Agriculture found that about a third of the additional calories provided by the sugar-sweetened drinks were not burnt off, less fat from the food was broken down by the body and less energy was needed to digest the meal.
They suggest this process could ‘prime’ the body to store more fat.
A sugar-sweetened drink consumed with a meal containing 15% protein cut the amount of fat oxidised by an average of 7.2g.
Fat oxidation describes the process in which the body uses up stored fats to produce energy.
If a sugar-sweetened drink was consumed with a 30% protein meal, fat oxidation decreased by 12.6g on average, the researchers found.
A Sealed Metabolic Chamber
The findings are based on 13 men and 14 women who were all of healthy weight and had an average age of 23.
All the participants spent two 24-hour periods in a special ‘metabolic chamber’ comprising an airlock system to allow meal trays and other materials to be passed in and out.
The sealed nature of the chamber allowed the scientists to assess how dietary changes affected energy expenditure, and the way nutrients were processed by the body.
During one stay, the participants were given breakfast and lunch consisting of 15% protein meals after fasting the previous night.
On their other visit, they had two 30% protein meals after fasting. The order in which the two protein levels were served was randomised.
All the meals were designed to provide 17g of fat and 500 non-beverage calories. The increase in protein was counterbalanced by a decrease in carbohydrates.
The principle difference was that the volunteers drank a sugar-sweetened drink with one of the meals and a non-sugar-sweetened drink with the other meal.
When the participants were fed more protein, they felt fuller and less likely to crave savoury, salty and fatty foods. After being given a sugar-sweetened drink with their protein-based meal, this appetite for savoury and salty foods returned.
Future Research
Dr Ian Johnson, a nutrition researcher and emeritus fellow at the Quadram Institute Bioscience, comments in a statement: “The work is unusual in that it was carried out under very precisely controlled laboratory conditions which make it possible to measure energy inputs and outputs with great accuracy.
“The results do suggest a mechanism whereby consumption of sugary drinks with meals might interfere with the body’s ability to regulate energy intake, and eventually lead to weight gain.
“However, for this to happen the observed effects would need to be maintained over an extended period of time, and the authors themselves are careful to point out that they have not yet shown this.”
SOURCES:
Postprandial energy metabolism and substrate oxidation in response to the inclusion of a sugar- or non-nutritive sweetened beverage with meals differing in protein content, Casperson S, BMC Nutrition
Science Media Centre
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