A high salt intake may be linked to obesity, regardless of how many calories are consumed, experts have suggested.
Writing in the journal Hypertension, researchers said there was suggestion of a link between how much salt a person eats and their weight, regardless of other factors.
But other professionals urged caution, saying the findings were unreliable because people in the study self-reported how much they ate.
The new research used data for more than 450 children and 780 adults from the UK National Diet and Nutrition Survey 2008/2009 to 2011/2012.
Experts analysed urine samples over 24 hours and calculated calorie intake from a four-day diary.
The results showed that salt intake in urine was higher in people who were overweight or obese, with an extra gram of salt a day leading to a more than 20% increase in the chance of being heavy.
"These results suggest that salt intake is a potential risk factor for obesity independent of energy intake," the authors said.
Susan Jebb, professor of diet and population health at the University of Oxford, said "there is no way to be confident" in the findings.
"Salt reduction is important to reduce cardiovascular risk but the combination of a weak study design and lack of any strong mechanistic basis for the association between salt and fatness means that this study should not detract from the main cause of weight gain which is consuming too many calories," she said.
"I would not want to see the public misled by the publicity around this paper into thinking that cutting salt alone will reduce their risk of obesity or help them to lose weight."
Graham MacGregor, professor of cardiovascular medicine at Queen Mary University of London and chairman of Consensus Action on Salt and Health, said: "The food we eat is now the biggest cause of ill health through its high salt, fat and sugar content added by the food industry.
"High blood pressure and obesity both lead to the development of cardiovascular disease, stroke, heart attacks and heart failure, which are the commonest causes of death and disability in the UK."
Victoria Taylor, senior dietitian at the British Heart Foundation, said: "It's well established that we should be reducing the amount of salt we eat to help avoid high blood pressure, a risk factor for cardiovascular disease and the link between salt intake and obesity identified in this research could be another reason for us to do this.
"But more research is needed to understand what might be the reason for this link.
"Most of the salt we eat is already in the foods we buy, which is why checking nutritional information on packs to make sure we are making the healthiest choice is important to help limit the amount of salt we are eating."