The fattest countries on average, based on adult obesity rates, are Pacific Island nations, with Tonga and Nauru consistently ranking at the very top, often exceeding 70% of their adult populations being obese, followed closely by the Cook Islands, Tuvalu, and Samoa, according to sources from WorldAtlas and the World Obesity Federation.
Although the prevalence of obesity in China is relatively low compared with Western countries such as the United States, where over half of adults are either overweight or obese, it is the rapid increase of the condition,4 especially among children, that is particularly alarming.
Seventy percent of Americans may now be classified as obese, according to a new study authored by Harvard Medical School researchers investigating an updated definition for obesity. This figure is up from 40 percent of the population who meet the old threshold for obesity, defined as a Body Mass Index higher than 30.
West Virginia topped WalletHub's 2025 ranking of the most overweight and obese states in the U.S., published Nov. 4, while Colorado is the healthiest-weight state.
The most overweight and obese US cities
Based on overall score, McAllen, Texas, was the most overweight city in the United States.
Percentage of obese U.S. adults by state 2023
The states with the lowest percentage of their population who are obese include Colorado, Hawaii, and Massachusetts.
Using data from UnitedHealth Group and the Health Action Council, the rate of obesity among Gen Z females was estimated to be nine percent. In comparison, around five percent of Gen Z males were thought to be obese.
Nearly half of adolescents and three-quarters of adults in the U.S. were classified as being clinically overweight or obese in 2021.
Under the new framework, a person is classified as having obesity if they have a high BMI plus at least one elevated anthropometric measure (a condition the authors term “BMI-plus-anthropometric obesity”), or if they have a normal BMI and at least two elevated anthropometric measures (a condition termed “anthropometric ...
Currently, BMI is the commonly used indicator to measure body fatness and health. Its computational formula is BMI = weight ( in kilograms) ÷ the square of height (in meters). The normal BMI range for healthy Chinese adults (18 to 64 years old) is 18.5 to 23.9. A BMI≥24 means the subject is overweight.
The traditional diet in Japan is built around a base of rice and other grains, with plentiful consumption of vegetables and fruits, and also fish, but relatively little animal fat, meat and sweets. In Japan, the presentation of the food is very important, and particular attention is given to the colors and textures.
Its latest figures, which are from 2016 but were only uploaded last month, show that the US healthy life expectancy is 68.5, and in China is 68.7. That means Chinese people get 73 days, or around 10 weeks, of extra healthy life.
The physiological mechanism causing the increase in obesity is no mystery: Americans eat more calories than they burn, and the excess energy is stored as fat. Greg Critser's book provides an insightful look at the reasons the energy balance equation has become so unbalanced.
Least Obese Countries by Population:
Obesity in China is a major health concern according to the WHO, with overall rates of obesity between 5% and 6% for the country, but greater than 20% in some cities where fast food is popular. A McDonald's Chinese New Year meal. American fast food outlets have been blamed for the increase in obesity in China.
Effects of lack of sleep:
A hormone imbalance in the body that promotes overeating and weight gain. Leptin and ghrelin are hormones that regulate appetite, and when you aren't getting sufficient sleep, the production of these hormones is altered in a way that creates increased feelings of hunger.
The vast majority of courts have held that obesity is not a disability under the ADA unless it is caused by an underlying health condition. Some federal district courts, as well as many state courts, have held that obesity is a disability even absent evidence of an underlying health condition.
They found that as physical activity increased, change in body weight decreased (i.e., individuals gained increasingly less weight over time), with the most active quintile being associated with a –1.86 pound reduction in body weight (i.e., individuals gained 1.76 fewer pounds within each 4-year period).
Generation Alpha is the largest generation, making up 24.4% of the global population. Gen Z and Millennials still hold strong influence, comprising 22.9% and 21.2% of the global population.
Gen Z youth, or “Zoomers,” have lower rates of smoking than adults from other age groups. They're also less likely to drink alcohol. The pattern holds when you look back in time: Today's Gen Z youth drink less than Millennials or Gen X kids did when they were young.
WASHINGTON, D.C. — After peaking at a record high of 39.9% in 2022, the U.S. adult obesity rate has gradually declined to 37.0% in 2025. This is a statistically meaningful decrease representing an estimated 7.6 million fewer obese adults compared with three years ago.
The most well-known is ghrelin, the 'hunger hormone', which is mainly secreted by the stomach. If you don't sleep enough, levels of that hormone will be higher, and you will feel hungrier and consume more calories. Over the long term, this leads to weight gain.
Easy access to trails, sunny weather and a highly educated population churning and burning more calories at altitude are all widely attributed to Colorado being the thinnest state.