Combined prevalence of underweight and obesity has increased in most countries since 1990, study reports

By Dr. Liji Thomas, MDMar 12 2024Reviewed by Danielle Ellis, B.Sc.

Excessive body weight causes multiple adverse health outcomes, as does being underweight. These range from emotional to social to physical health.

As a result, nutritional and health policies must address underweight and obesity, pursuing Sustainable Development Goal Target 2.2 ((ending all forms of malnutrition). A new study in The Lancet looks at their worldwide impact on the prevalence of obesity and underweight from 1999 to 2022.

Background

There have been differing trajectories for both these forms of malnutrition, but not much data on how their combined prevalence has changed. There is also a need to know their individual prevalence.

The obesity epidemic is well-known but equally important in public health is the underweight epidemic. The type and amount of food now available have shifted dramatically, a change called the nutrition transition. Similarly, in several countries, the population-based body weight shifts from underweight to obesity – the obesity transition.

This is the focus of the current study, which may help “bridge the gap between knowledge and policies focused on undernutrition and obesity.”

Introduction to the study

The study used data from almost 3,700 studies that covered 222 million participants. These studies represented the general population. However, the data distribution was non-uniform. While Western English-speaking and European countries had a mean of almost 50 studies per country, there were only 5 per country from Oceania and <8 from sub-Saharan Africa.

Changes in double burden: adults

The researchers found that the prevalence of both obesity and underweight went up globally. In all countries, the 2022 double burden exceeded 10%. Among women, the combined prevalence increased in over 80% of countries, while among men, it increased by 70%.

Polynesian and Micronesian nations were among those with the highest prevalence of the double burden, at over 40%. Most of the malnutrition was in the form of obesity.

Conversely, India and Bangladesh also showed a high double burden, driven by the prevalence of underweight. They also experienced large declines in the double burden, by 33 and 22 percentage points among women and men in Bangladesh and India, respectively.

In 2022, for almost 90% of countries, obesity was more prevalent among women than underweight for women, vs. 73% of countries for men. The greatest increases in the obesity burden were in South Asian and West African countries.

In 50 countries, the double burden shifted to become obesity-dominated from underweight-predominant. Again, by 2022, over 90% of the combined burden was due to obesity in 34% of countries for women but 44% for men.

The combined prevalence went down among women over the study period in only 6% of the countries, vs 9% for men. The prevalence of underweight was higher than that of obesity in only 8% vs 20% of countries for women and men, respectively. In most cases, the reduced double burden was due to the falling prevalence of underweight rather than obesity.

Changes in double burden – children

Over this period, girls and boys in 70% of countries had a higher double burden. It went down in 3% and 8% of countries for girls and boys, respectively.

It was highest in the same island countries that showed the highest prevalence of obesity among adults. For boys alone, it was highest in Chile and Qatar. Interestingly, in India and Pakistan, the prevalence of thinness declined but remained high, contributing to a high combined prevalence.

In 2022, school-age children and teenagers of both sexes were more likely to be obese than thin, at 67% and 63% for girls and boys, respectively. The opposite was observed in 18% and 20% of countries for girls and boys, respectively.

Changes in underweight

For almost all countries, the increase in combined thinness and obesity was driven by increasing obesity. Decreases were due mostly to declining rates of underweight. In 65% of the countries, women were less underweight by 2022 vs 75% for men.

The greatest decline was in South Asia, including India and Bangladesh, and Southeast Asia, including Vietnam and Myanmar. Alone in this survey, women in Japan and South Korea showed an increase in underweight.

The decline in underweight was most marked in those countries with the largest burden in 1990. While the lower prevalence of being underweight is something to celebrate, it remains high in some African and South Asian countries. This can be mitigated through improved access to healthy foods, dietary education, and programs to prevent obesity.

Changes in obesity

Obesity among adults increased over the study period in almost all countries. Most affected were some sub-Saharan countries in Africa for women, while for men, it included the USA, Brunei, some central European countries, and Polynesia and Micronesia.

Large increases of over 20 percentage points occurred in almost 50 countries for women and 24 for men. The greatest rise of over 31 percentage points occurred in the Bahamas among women and in Romania among men.

Reductions in obesity occurred only among Spanish women and French men. No association was observed with the baseline level of obesity in 1990, unlike for underweight.

Less than 5% of women and men were obese in only six vs 17 countries, respectively. In contrast, >60% of women and men were obese in eight vs men in six countries, respectively.

What are the implications?

Overall, the double burden of obesity-underweight malnutrition has gone up in most countries. Decreases in the burden were mostly because of the falling prevalence of underweight. Rising obesity rates drove increases in the burden.

In certain countries, obesity rates exceed those in industrialized countries. “The transition to obesity was already apparent in adults in 1990 in much of the world, as demonstrated by the large number of countries in which adult obesity exceeded underweight at that time, and has since followed in school-aged children and adolescents.”

This followed the nutrition transition, with greater dependence on commercially prepared processed foods that have lower nutritional quality. Caloric consumption, sugar intake, meat consumption, vegetables, and oil consumption have increased in many poorer countries. In contrast, meat and sugar consumption are falling in richer countries.

Notably, food programs and agricultural policies in some countries improved the diet quality and led to increases in height. Conversely, weight gain without an increase in height caused obesity, especially since research indicates reduced basal adult energy expenditure at present.

The need of the hour is the development of programs to prevent obesity. These should target both individual behaviors and economic and agricultural policies aimed at weight loss and improved access to healthy foods.