Speaking at an educational session on sweetener science at the IFT show in Chicago on Sunday, Warshaw said the media often treated prospective cohort studies in a very similar way to randomised controlled trials (RCTs). Cohort studies are often used to examine dietary patterns and correlations with health outcomes, while RCTs are considered the gold standard in nutrition research, allowing scientists to assess the impacts of specific dietary interventions.
As a result, correlations between high consumption of non-nutritive sweeteners and higher body weight – found in many cohort studies – tended to be misrepresented as causational, she said.
“The core of these negative [media] reports stems from prospective cohort studies, but the results have been mixed. Some show increased body weight, some show decreased body weight, and others show both,” she said, citing a recent review of the evidence from such studies.
However, the same review found that randomised controlled trial results showed low- and no-calorie sweeteners did indeed help reduce body weight, BMI, fat mass and waist circumference.
Benefits beyond weight loss
RCTs also had found benefits to non-nutritive sweeteners beyond weight loss and maintenance, she said, including greater adherence to a diet plan for those consuming diet drinks as opposed to water to replace sugar-sweetened beverages in their diet, and greater likelihood that participants would achieve a 5% weight loss within six months.
A separate analysis of this trial found that those who drank diet drinks also had a bigger reduction in their dessert consumption than those who drank water.
Warshaw suggested that correlations between diet drink intake and higher BMI from cohort studies may be because people at risk of overweight or obesity were more likely to use low- and no-calorie sweeteners as a tool to help manage their weight.
She also highlighted the US National Weight Control Registry, which is the world’s largest study of successful weight maintenance. Established in 1993, it examines the behaviours of people who have lost at least 30 pounds (about 13.6 kg) and have kept it off for at least one year. “Fifty-three per cent regularly consumed low calorie sweetened beverages compared to 28% of the general population,” she said.
Warshaw also questioned whether some people may have a natural preference for sweeter foods and drinks and called for more research in this area.