The percentage of US adults who are obese increased in 2014 to reach 27.7 per cent – up from 27.1 per cent in 2013 and 25.5 per cent in 2008, according to the Gallup-Healthways Well-being Index study.

Based on more than 167,000 interviews conducted in 2014, respondents’ self-reported height and weight measurements were used to calculate body mass index (BMI) and led to the highest obesity rate measured by Gallup in seven years of tracking it.

More Americans who were previously overweight have now moved into the obese category, while the percentage of people who are at a normal weight ratio has remained stable since 2013.

The percentage of underweight Americans has remained steady at 2 per cent.

The Gallup-Healthways Well-being Index measures the five essential elements of wellbeing: purpose, social, financial, community and physical. The index is calculated on a scale of 0 to 100.

The report found that although the obesity rate among black people has not changed much since 2008, this group has the highest obesity rate of any major demographic group at 35.5 per cent. Obesity rates also exceed 30 per cent among Americans aged 45 to 64 and those earning less than US$36,000 (€31,743, £23,871) per year. Young adults aged 18 to 29 years old are the least likely to be obese, at 17.7 per cent, followed by those earning at least US$90,000 (€79,369, £59,700) per year – at 23.1 per cent.

These results reinforce Gallup’s previous findings: that obese adults experience lower social wellbeing than their mean-weight or overweight counterparts, plus higher obesity rates are linked to lower incomes and long-term unemployment – reinforcing the relationship between obesity and lower wealth.