Highlights
- More than 2 billion people are thought to be obese today worldwide.
- In recent decades, the global bulge has increased at a rapid clip.
- Obesity is now one of the largest contributors to poor health worldwide.
- New evidence prompts researchers to propose obesity as a “neuro-developmental” disorder.
Is the world getting really fatter? The answer is a straightforward “Yes”.
In 2022, Obesidemic: Weight of the World, a fascinating documentary that looks at obesity, was released on IMDb. In the 80-minute film, Stockholm-based obesity specialist Dr. Stephan Rossner sought to prove that obesity is a “man-made epidemic”. For one, it’s dubbed as a health “timebomb”.
Consider this: In 2022, more than 1 billion people worldwide were considered obese, broken down as follows — 650 million adults, 340 million adolescents and 39 million children.
World Health Organisation (WHO) data shows being overweight is seen behind 2.8 million deaths each year; a number set to rise.
Obesity is seen overtaking smoking as the leading risk factor for avoidable cancer in several nations. It is known to have negative impacts on blood pressure, cholesterol, triglycerides, insulin resistance, and general quality of life.
Q: What do we know about the factors behind the emergence of “obesogenic”?
The risks of obesity are well established, but the causes are not as well understood. Obesity risk is generally ascribed to two factors: environmental and genetic. A new third factor is emerging: neuro-developmental. Let's break them down.
1. Environmental factors
It’s down to lifestyle. Specifically, present-day eating habits. One question to ask is this: Why were there so few obese people up until the 1960s and 1970s?
In the last few decades, the rise of industrial agriculture producing raw food ingredients at very low cost per calorie output, has no doubt resolved global hunger. One unintended outcome: an overabundance of food. As globalisation advances, ingredients can be sourced from anywhere where production costs are lowest or heavily subsidised.
Moreover, urbanisation, labour-saving tech, app-driven take-aways of “super-sized” portions, alongside a multi-billion ad industry working with food companies that produce highly palatable and durable foods — smothered in sugar, salt and fat — together work for a waistline-busting affair.
Hypermarkets, too, have mushroomed with an abundance of processed foods, lower prices through their bulk purchasing power — aided by data-driven promos.
On a personal level, people have less time for sourcing, preparing and eating food. One study published in the Nutrition Journal shows that since 1965, US adults have consumed fewer foods produced at home and spend less time cooking.
Between 1965-1966 and 2007-2008, the percentage of daily energy taken from domestic food sources and time spent in food preparation declined dramatically for all socioeconomic levels, with the greatest decreases occurring between 1965 and 1992.
How to change the food environment? One solution proposed is via legislation — similar to tobacco controls and sugar tax in increasing number of jurisdiction, specifically geared towards salty and fatty processed foods.
In response, the food industry has unleashed “ready-to-heat” meals, “ready-to-eat” snack foods and “fast-food” outlets.
Dealing with the bulge is made more difficult in this type of climate — it's like attempting to drive personal responsibility, including in children, in an environment meant to undermine it.
For example, many child-oriented food products – notably yoghurt, drinks, breakfast cereals and dried fruit snacks – bear statements such as “no added sugar”. They come with bright and colourful packaging marked with cartoon designs to catch the eye of children, with claims about health benefits such as the presence of calcium or the addition of vitamins and nutrients.
While the “no added sugar” claim is technically true, these claims are misleading, the Daily Telegraph stated in a August 2022 report.
It concluded: “The most frequently reported sphere of action targeting children and adolescents was marketing and preference shaping.”
The NIH study has identified “commercial determinants of dietary behaviour associated with obesity… as being part of a complex system where corporate practices are enabled by power structures.”
It suggests a careful and systematic study — specifically on the “impact of specific aspects of food industry's strategies and increase primary prevention by anticipating industry responses and by discouraging corporate practices that harm health.”
How to change the food environment? One solution proposed is via legislation — similar to tobacco controls and sugar tax in increasing number of jurisdictions — specifically geared towards salty and fatty processed foods.
2. Genetic factors
Genes do not work in isolation from the environment, but they do have a role in obesity risk factors. According to a Harvard research, most people "certainly have some genetic propensity" to obesity, depending on family history and ethnicity.
The gene MC4R, which encodes the melanocortin 4 receptor, is the most frequently implicated. Changes in MC4R function are seen in a modest percentage (5%) of obese adults from various ethnic groups. Children who are affected feel exceedingly hungry and develop obese as a result of their frequent overeating (hyperphagia).
Using genome-wide association analyses, researchers discovered the first obesity-related gene variations in the "fat mass and obesity-associated" (FTO) gene on chromosome 16.
These gene variations, however, are relatively "common", the Harvard medical report stated. People who have one have a 20% to 30% greater risk of obesity than those who do not.
• Across 12 chromosomes, researchers discovered more than 30 candidate genes linked to BMI.
• Even FTO, the most promising of these candidate genes, however, explains only for a modest proportion of the gene-related predisposition to obesity.
But moving from genetic susceptibility to obesity usually necessitates some modification of nutrition, lifestyle, or other environmental factors. Again, the elephant in the room is the environment — the circumstances that determine how much we eat and how active we are.
"Heredity is not always destiny," the Harvard School of Public Health research stated. “Environmental changes that make it easier for people to overeat, and harder for people to get enough physical activity, have played a key role in triggering the recent surge of overweight and obesity."
3. Neuro-developmental factors
A third factor suggested is neuro-developmental, related to the second one. Recently, a team led by Van Andel Institute scientists identified two distinct “sub-types” of obesity in a study.
In their findings, published on September 12, 2022 in the journal Nature Metabolism, researchers sought to redefine and further refine understanding on obesity.
Using a purely data-driven approach, researchers led by J. Andrew Pospisilik, Ph.D., chair of Van Andel Institute's Department of Epigenetics, found that each of metabolic subtypes of obesity has their own physiological and molecular features that influence health.
One obesity subtype is characterised by "greater fat mass"; the other was characterised by "both greater fat mass and lean muscle mass", the researchers found.
After the two subtypes were identified in the human data, the team then verified the results in lab mice models. The second type also was associated with increased inflammation, which can also elevate the risk of certain cancers and other diseases.
Both subtypes were observed across multiple study subjects, including in children. Interestingly, it also revealed that the second, inflammatory subtype appears to result from changes triggered by “pure chance”, what researchers refer to as "unexplained phenotypic variation" (UPV).
There was no gradient in the size of the genetically identical brother mice; they simply grew to be larger or stayed smaller. Data from more than 150 human twin pairs, each of which had nearly the same genetic makeup, revealed a similar pattern, according to the study.
That implies that something else may be in charge of up to 50% of who we are. According to the study, "epigenetics" (the mechanisms that control when and how the instructions in DNA are used) is likely where the origins of UPV reside.
• In other words, it focuses on the changes in organisms caused by modification of gene expression — a system known as molecular “bookmarking” — rather than alteration of the genetic code itself.
• This “bookmarking” determines which genes will — or will not — be used in different cell types.
• Identical twins offer a good example of epigenetics: Although they share exactly the same DNA, their unique experiences in life will cause some genes (and not others) to express themselves. So, over time, identical twins come to look and behave differently.
So what accounts for rising global “obesidemic”?
Genetic changes are unlikely to explain the current global epidemic of obesity. To blame genes alone, or the environment alone, or the neuro-developmental factors alone for this phenomenon misses glaring present-day realities. It's a multi-factorial challenge.
The human "gene pool," or the frequency of different genes in a population, across many generations, has been relatively stable for thousands of years. It takes a long time for new genetic mutations, known as “polymorphisms”, to spread in the human population.
So then if our genes have virtually remained unaltered during the past 50 years amid rising obesity rates, the only thing that has really changed is the easy availability of sugar-packed, high-carb foods, 24-hour TV, gaming, Youtube, and other such "obesidemic" factors.
