Four in five students in a Leicester study drank sugary drinks, a third got a tenth of their energy from free sugars. Their body fat didn't give it away

Most of what we know about sugar and weight in young adults comes from broad categories. A survey box marked 'soft drinks' can hold a regular cola, a diet cola and a sports drink, which makes the answers hard to read. A study published in Nutrients on 28 October, from researchers at De Montfort University in Leicester and the University of Alcalá in Spain, tried to be more precise about where the sugar was actually coming from.

The data are not new. In January to mid-March 2016 the team assessed 111 students aged 18 to 22 at De Montfort University. Seven in ten were women, and the group was unusually mixed: 37% were born in Africa, 37% in Asia and 24% in Europe. Each filled in a food-frequency questionnaire covering the previous four weeks, adapted from the one used in the long-running EPIC-Norfolk study, and had their height measured by a nurse and their weight and body fat measured on a bioimpedance scale after an overnight fast.

For this analysis the researchers went back to the raw records and checked all 441 food and drink names one by one. Regular soft drinks, squash and cordials, sports drinks, energy drinks and sweetened fruit drinks counted as sugar-sweetened drinks. Diet and zero-sugar versions did not, and neither did 100% fruit juice, which was tracked separately even though its sugars count as free sugars under UK and WHO definitions. Three drinks whose recipe in 2016 couldn't be pinned down were left out and tested separately.

The median student got 43.2 g of free sugars a day, 8.2% of their energy. A third (33.3%) were at or above 10%, the WHO's upper limit, and fewer than one in five (18.9%) were below 5%, the stricter UK target. Four in five (81.1%) drank sugar-sweetened drinks, a median of 159 g a day by weight, about half a standard can. Regular soft drinks and cola made up 62.3% of all of it, squash and cordials 19.4%, sports drinks 9.3%, energy drinks 5.6% and sweetened fruit drinks 3.3%. Most students (83.8%) also drank some 100% juice.

Then the question everyone wants answered: did the students with more sugar carry more fat? None of the six main comparisons found a clear link with BMI, body fat or the scale's visceral fat score, after allowing for age, sex, birthplace and total calories. The authors are explicit that this is not evidence of no effect. Each 5-point rise in free sugars' share of energy went with 0.5 points more body fat, but the range of plausible values ran from 0.7 points less to 1.7 points more. With 109 people in the models, the study couldn't rule a meaningful effect in or out.

There are other reasons for caution. It is a one-off snapshot, so it can't show cause and effect. Food-frequency questionnaires rely on memory, and this expanded version was not re-checked against a reference method. The students were young and mostly lean (average BMI 23.7), and visceral fat scores ranged only from 1 to 9, all inside the device's normal range, which leaves little room to see differences. The authors also stress the date: the UK's Soft Drinks Industry Levy arrived in April 2018 and pushed manufacturers to cut sugar from many drinks, so these figures describe what students drank before that change, not what they drink now.