(CNN)The world is in the middle of a major obesity epidemic, and current trends indicate that it's only going to get worse.
A recent study found that more than 2 billion adults and children globally are overweight or obese and suffer health problems because of that -- but this is nothing new.
There are, however, pockets of the global population who remain somewhat unaware of this public health crisis, despite the growth of waistlines all around them, and this lack of awareness is just one of the underlying problems, according to Frank Hu, professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health.
"Different countries have different issues," Hu said. "You need to mobilize (their) whole society to tackle the problem. ... it's not just a medical problem."
The Pacific Islands, Middle East and Americas lead the way in terms of regions with the greatest obesity rates. In 2014, more than 48% of the population of the Cook Islands was classified as obese. Qatar led the way in the Middle East with 34%, followed closely by the United States at 33%, according to the World Health Organization.
Obesity is defined using a person's body mass index, the ratio between weight and height, with a BMI of 25 to 29.9 considered overweight and over 30 obese.
When assigning blame, two factors are common: diet and physical activity, namely poor diets and a lack of physical activity. But a number of smaller factors combine to fill these two large umbrellas, and those need to be understood to truly tackle the problem, Hu believes.
What is behind the obesity problem among countries at the top of the table?
1. Activity inequality
A study published this week in the journal Nature used data from smartphones to analyze the number of steps taken on average each day among people across 111 countries.
Using the Azumio Argus app, which tracks physical activity, researchers monitored the steps of more than 700,000 individuals and ranked countries based on their level of movement in the form of steps -- and those numbers varied quite significantly.
Hong Kong topped the rankings with 6,880 average daily steps, followed closely by China with 6,189 steps. At the bottom of the list was Indonesia, with 3,513 steps.
However, the researchers calculated another statistic that they believe is a stronger predictor of obesity within a country, a calculation they called "activity inequality."
"Activity is not distributed uniformly across a country," said Scott Delp, professor of bioengineering and mechanical engineering at Stanford University, who led the study.
The larger the difference between the top and bottom walkers within a population, the greater their rates of obesity are likely to be, he explained. "It means there is a subset of a population that is activity-poor."
When focusing on activity inequality, the list changed, with Saudi Arabia and Australia ranking first and second. The US came in fourth, with levels of activitygreatest in more car-oriented cities like Houston and lowest in more walkable cities like New York.
1. Saudi Arabia
5. United States
The team also found this inequality to disproportionately affect women, meaning more women would be in the "activity-poor" subset of the population. "Targeting the activity-poor (could) have a public health impact," Delp said.
2. Perceptions of exercise
While physical inactivity is said to be aiding the growing rate of obesity worldwide, for example as urbanization leads to more sedentary lives, experts point out that in some populations, exercise simply isn't a priority.
This is evident in the Middle East and China, they say, namely through perceptions of exercise and its place on residents' list of priorities.
In Kuwait, focus groups from the World Health Organization found that locals consider exercise as sport rather than something done with a group of friends or at home, according to Temo Waqanivalu, team leader of population-based prevention of noncommunicable diseases at the WHO. "There's a whole cultural barrier," he said.
In addition, in the Middle East overall, it's not considered the norm for women to take part in outdoor exercise or physical activity for leisure. "Having women exercise openly is a cultural issue," he said.
Across Asia and the Middle East, Hu thinks there is a great deal of misunderstanding. "Most people are not aware of the benefits of being physically active on their health," he said.
3. Poor prioritization of exercise
In China, however, and other parts of East Asia, an extensive focus on academic achievement can often mean physical education is left behind. Students "are under tremendous pressure for academic achievement," Hu said. Physical education "classes are often used for academic studies."
Hu further cites Japan and the countries of Scandinavia, where exercise is a common part of daily life in terms of commuting and socializing. In Japan, he said, "it's encouraged ... in older age."
4. Environmental factors
Another factor hindering exercise in many places is the outdoor environment. In the Middle East, that means temperature.
"It's typically very hot to do outdoor activities," Hu said. The same is true in many developing regions near the equator, and when combined with poor perception of exercise and lack of awareness of its importance for health, the impact is more significant.
In China, the issue is pollution. "Pollution has become a burden to exercise outdoors," Hu said. This is particularly problematic for children and the burgeoning childhood obesity epidemic, studies have shown.
But Waqanivalu believes that people's eating behaviors are in more dire need of attention.
"It's now understood that ... food and diet is a bigger contributor (to obesity) than a lack of physical activity," he said. And within this comes a combination of culture and environment fueling poor dietary behaviors -- and therefore overweight and obesity.
5. The value of (processed) food
The value placed on food varies significantly among populations, but one thing most have in common is gifting and an expression of generosity using food -- and, therefore, value placed on the type of food given.
In the Pacific, where obesity rates are highest, processed foods hold high stakes.
"For every ceremonial function in the Pacific, you bring food," said Waqanivalu, himself a native of Fiji. "There has been a shift in the types of food in that exchange."
Offerings would once be freshly caught fish or fresh fruit, but they are now canned or processed foods. "You hear ... people would go and fish, sell their fish and buy cans of tuna," he said, adding that being surrounded by fish seems to lessen their value.
"Canned foods come with prestige in some way," he said. But he believes that education and awareness efforts by the government in recent years may now slowly be paying off.
Similar attitudes have been noted in parts of the Americas -- such as Brazil, where soft drinks and processed foods also carry weight as signs of wealth and success -- as well as Africa. "They have an abundance of local food (in some places) but have cultural value attached to (processed foods)," Waqanivalu said.
In the Middle East, extreme wealth means people are consuming greater amounts of high-calorie foods, adding to weight gain. "The abundance of energy-dense foods is remarkable," Hu said.
6. The value of obesity
Societal perceptions of being overweight or obese are also key in determining how effectively an obesity epidemic may surge and in turn be controlled.
Hu uses the example of China and other regions within Asia as well as Africa, where having a larger, more robust figure remains a sign of wealth. The idea of a chubby baby being a sign of wealth and health in China, for example, "hasn't fully gone away yet."
"There is less social stigma about being obese," Hu said. "May don't consider obesity as a major problem."
7. An obesogenic environment
"The food and physical environment are key factors that we have created," Waqanivalu said, adding that while initial blame was placed on individuals, experts have now agreed that as a society, we have created environments that aid people in gaining weight.
"The environment created determines the choices individuals make," he said. Sitting most of the day, taking fewer steps, having greater access to fast food and having less time to cook are just a few examples.
The US is a prime example of this and has been for 30 years. "The US is still the superpower of obesity," Hu said, highlighting the availability of cheap, highly processed foods and urban design focused on driving -- particularly in the South and Midwest. "The obesity trend has been very stubborn over the past three decades, despite efforts."
But today, as developing regions rapidly urbanize and adopt a lifestyle like the West has had for decades, individuals are directed to make the same decisions: They need to try harder to take more steps and go in search of healthy food, ignoring the unhealthy options bombarding them on the way.
"In Africa, it's certainly true ... and the Americas," Waqanivalu said. "Why do we bring these foods in and then teach the population not to eat them?"
Tackling the causes
Waqanivalu and Hu agree on this point and the fact that interventions are needed to counter decisions previously made on environmental design as well as highlight the true extent of today's obesity epidemic and its future consequences to those not taking an interest.
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Hu believes that obesity is truly a societal, not individual, problem and that national and international policies are needed to create settings in which it is easy for people to be healthy.
Waqanivalu believes the priority should be children.
The number of overweight or obese infants and children under the age of 5 increased from 32 million in 1990 to 42 million in 2013, according to the World Health Organization, with numbers increasing from 4 million to 9 million in the African region alone over that period.
"(Children) cannot be blamed for the environment they are raised in," Hu said. "Governments must intervene to create an environment that aids them to make the right decision."