The UK health secretary, Wes Streeting, has said that if everyone who is overweight reduced their food intake by 216 calories a day (equivalent to a single bottle of fizzy drink), obesity rates would be halved, while cutting 50 calories a day would lift 340,000 children and two million adults out of obesity.

However, the BBC’s More or Less radio programme – produced in partnership with the Open University – has disputed the 216 calorie figure in a recent broadcast.

UK’s 10-year public health strategy

The claim was made as the government unveiled England’s 10-year public health strategy, which has been designed to encourage food businesses to make it easier to reduce the population’s sugar and calorie intake.

The BBC’s More or Less investigation

The BBC investigation found the research the government was quoting in making its claim is much broader in scope.

The analysis covered caloric reduction in people with obesity as well as people who were overweight but not obese.

It showed that if this entire – much larger – cohort reduced calories by 216, rates of obesity would be halved.

The modelling was carried out by a charity that supports innovation, called Nesta. Its analysis was focused on how much weight we’d have to lose to get our waistlines back to the size they were in the early 1990s – when obesity rates were about half what they are now.

Dr Kevin Hall

The BBC interviewed Dr Kevin Hall, a prominent researcher in the field of metabolism, obesity and nutrition because his weight loss model (developed in 2011) is what Nesta used in its calculations.

The model helps to calculate how the energy needs of the body change as people lose weight.

He said that Nesta applied the model correctly for its purposes, but that in reality, human physiology makes understanding the impact of such a calculation more complicated.

Appetite

Hall was keen to point out that his model doesn’t adjust for human appetite.

He described a 2016 study where people were given drug designed to treat diabetes that secretly lowered calorie intake.

However, the body compensated because participants’ appetites increased.

“For every kilogram of weight they lost, they wanted to be eating about 95 calories a day above their baseline needs,” said Hall.

An intervention, such as a constant deficit of 216 calories, is fighting an increasing battle against an increase in appetite.

“To maintain increased levels of weight loss, you have to put up with increasing levels of hunge, as appetite attempts to get people back to their original state,” added Hall. “So people eat more calories as they lose weight until the effects level out.”

Hall said that if someone were looking to sustain a 216-calorie deficit, they would need to start by cutting around 1,000 calories per day, because after a year, appetite will cause the weight-loss effects to wane to around a deficit of 216 calories per day.

His research suggests you need a big cut in calories to seriously change weight if this is all you do to lose weight.

Nesta agreed that the policies the government wants to introduce may not have the desired effect. The organisation said, however, that if the new plan can achieve at least a tenth of the reduction in obesity rates hoped for, implementing it will still be beneficial.