Cross curricular Biology article: Is it temperature or income which affects the percentage of obese people in countries?

Figure 1: https://ourworldindata.org/grapher/share-ofadults-defined-as-obese

Is it temperature or income which affects the percentage of obese people in countries?

It is commonly known that people are healthy because of the lifestyle they live and the amount of exercise they do. However, it is not commonly known that the weather can influence how effective exercise can be, and whether people have an advantage based on where they live and what the weather is like. In this article, I will be exploring whether there is a link between fitness and climate, and why people living in colder climates are potentially fitter.

When answering this question, we must first understand why there could be a link. One of the most effective and common ways of burning calories and staying fit is by exercising. People exercise passively walking every day, running, and cycling, or they could specially exercise, for example by going to the gym or swimming or playing outdoor sports. Whatever, it is, calories will be burnt when doing these various exercises. However, it has been found that exercising in colder conditions could result in more calories being burnt, which leads to the question of whether people living in colder temperatures would be fitter and less obese.

The human body has two types of fat, white and brown. White fat (white adipose tissue) is the most commonly known fat, as white fat is what causes obesity, which leads to other health problems. It stores energy in large fat droplets, and the accumulation of fat keeps one warm by giving insulation. Brown fat (brown adipose tissue (BAT)), is more compact and stores energy in smaller spaces compared to white fat. The reason why it is brown is because it is filled with mitochondria. Thermogenesis is where the body generates heat to keep warm. There are two types of thermogenesis: shivering and non- shivering. In shivering thermogenesis, the body shivers. Kinetic energy is required for the body to make shivering movements, and this is gained from the conversion of ATP to ADP, and through this process heat is produced. This does not burn many calories at all. Non- shivering thermogenesis happens in BAT. The burning of brown fat not only produces heat, but burns many calories. Clearly, having more brown fat will result in more calories being burnt, so people with higher levels of brown fat will burn calories more easily, hence they more likely not be obese.

One of the way of having more BAT in the body is by being in colder temperatures, as the colder temperatures stimulates stem cells to divide and form brown fat

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Figure 2

rather than white fat. It is clear to see here that colder temperatures have an influence as to how many calories one will burn, and this can be explored in the real world, to see if this is the case.

As you can see in Figure 1, the percentage of people who are obese in the world does not translate to the trend that people in colder countries are less obese. An explanation for this is the lifestyle in which the people in colder countries live in. For example, in European countries, most of them live a rich lifestyle and have a large income compared to less income countries. These countries have a luxurious lifestyle, such as cars, rich foods, jobs which do not require hard labour, and more. This will inevitably result in people exercising less and putting on more calories, so even if they have higher percentages of brown fat due to the cold temperatures they live in, their lifestyles far outweigh the effect brown fat may have. In Europe in 2016, the percentage of obese people in each country was over 18%, while in continents such as Africa and Asia the percentage of obesity in each country was generally between 0% and 10%. One could even argue that it is the cold climate which has made people fatter in these colder nations. Colder temperatures may discourage people to go out as much or exercise as much as it is difficult to exercise in low temperatures, so they will generally move less, and increase their number of calories. Hotter temperatures usually encourage people to go out more and do things, which is an explanation why the countries in central Africa have low obesity rates.

However, this doesn’t account for the American continents both north and south, where the percentage of obese people in the countries are over 18%. It is generally known that these countries have high levels of income and low levels of laborious work, especially in the Southern American countries, so this suggests that it is income which determines how obese a country is.

Nevertheless, if we look at Figure 2, the world in general was generally far less obese in 1975, and the European countries had a decreased percentage of obese people, but they still had a greater income and had richer lifestyles than the poorer countries, hence there is still a subtle disparity in obesity between these countries. Without the rich incomes, it can still be seen that the people in colder countries could be inherently thinner, as for example in the 1960’s, the percentage of obese people was around 1%, while in 2010 it was 25.2%. However, this still doesn’t establish a trend that colder countries have fewer obese people because it is easier to burn BAT.

To conclude, there is a clear link between it being easier to burn more calories in colder temperatures because of the increased ease of producing and burning brown fat, which burns more calories and in turn decreases the chances of becoming obese. However, the effects of having a high income and a rich lifestyle wipe out this inherent advantage in combating obesity, and the attraction of exercising and moving less, and eating more overweighs the physical advantage people in these colder countries may have.

References 1. Healthline. (2018). Brown Fat: How to Increase, Thermogenesis, and More. [online] Available at: https://www. healthline.com/health/brown-fat#How-toget-brown-fat. 2. Wikipedia. (2021). Thermogenesis. [online] Available at: https://en.wikipedia. org/wiki/Thermogenesis#Shivering 3. Ritchie, H. and Roser, M. (2017). Obesity & BMI. [online] Our World in Data. Available at: https://ourworldindata. org/obesity. 4. Wardrop, M. (2010). Obesity rates “20 per cent higher now than in the 1960s.” www.telegraph.co.uk. [online] 25 Feb. Available at: https://www.telegraph.co.uk/ news/health/news/7307756/Obesityrates-20-per-cent-higher-now-than-inthe-1960s.html

Plastic pollution of our oceans: who turns the tide?

Ben

By 2050, it is estimated that there will be more plastic than fish (by weight) in the ocean. Defined as ‘the accumulation of plastic objects and particles in the Earth’s environment that adversely affects wildlife, habitats, and humans’, plastic pollution, and how to tackle it, is increasingly becoming an issue that must be addressed by governments and environmental agencies around the globe, yet thus far attempts to end our love affair with plastic have been futile and far from sufficient. The health of the our most diverse ecosystem is deteriorating frighteningly fast and we must look for a global solution to this global problem. Plastic is inexpensive and longlasting – a perfect material for humans to commandeer, thus is ubiquitous in our everyday lives, yet its polymer structure renders it extremely resistant to erosional processes, so most plastics produced will take thousands of years to naturally biodegrade. That said, the most harmful plastics to

both marine life and ultimately humans are smaller than a single letter on this page. Microplastics, particles of plastic less than 5mm1 in diameteri, plague our oceans and are continuously ingested by marine animals, who are in no way adapted to breakdown these synthetic molecules, which, like the larger, more obvious macroplastics, do not readily decompose into smaller, harmless molecules. In fact, their size makes them more potent, infiltrating into marine animals undetected. To further complicate matters, microplastics in the ocean can bind with other chemicals, including food, before being ingested by marine

organisms. Each year, over 1,000,000 marine mammals are killed as a direct result of plastic and millions more face liver and cell damage as well as reduced fertility, potentially shrinking future generationsii. And it is not just marine life that is affected, 90% of seabirds have plastic as a regular component of their diets, both by direct consumption of mesoplastics, mistaken for food, and also indirectly by microplastics in fish and seawateriii . Microplastics are present in commercial seafood throughout the world, virtually unregulated, in alarming levels and cannot be completely removed in water purification facilities, thus are in circulation in our water supply. Though the dangers posed to humans aren’t fully understood, the consequences of consuming artificial, tenacious fibres are unlikely beneficial.

Of the 380 million tonnes of plastic produced annually, roughly 9% is recycled and a further 12% incineratediv (which poses its own negative environmental repercussions, producing toxic rubbish that enters these glorified bins can often be transported by the factors listed above into the nearby ocean within hours. In the UK, there are 1200 landfill sites that are close enough to the ocean to warrant a concernv. Whilst this was acknowledged in February 2020 by the UK government, no actions have been taken, epitomising the attitude that has plagued us for far too longvi. New regulations must be created to stop these landfill sites polluting the ocean, enforced by strict fines/ sanctions. The government should pay for the cost of removing these landfill sites, then relocating them to safer areas inland, regardless of the economic

greenhouse gases, in this case mainly carbon dioxide and carbon monoxide, and contributing to the enhanced greenhouse effect) whilst much of the remaining 79% ends up in landfill. As for future production, exponential increases are expected, doubling by 2050ii . Whilst direct littering into the ocean plays a significant role, most of the pollution (i.e transfer from land to the ocean) occurs via natural processes - storms, water runoff and wind. Landfill/ dumping areas close to the sea require reform – benefits of doing so – frankly, the health of our environment must take priority over the balance in our bank accounts.

Ever-improving technology will undoubtedly result in stronger, more durable plastics lasting longer and causing more damage to the ocean ecosystem. But it doesn’t have to be this way. Instead, capital should be invested into companies pursuing biological polymers (biopolymers) which can be broken down by natural

erosional processes/ enzymes and microbes. Many unbranched polymers derived from alkenes (example: polyethene – plastic bags) can easily be ripped but on a micro level, doesn’t fully decompose thus is not an ideal material for single use plastic bags. Biopolymers such as Polyhydroxyalkanoates (PHAs) and cellulose-based plastics readily decompose fully and are limited only by their production cost and unavoidably weaker structures. Research is being conducted by companies such as ‘Chroma Color Corporation’, ‘US Plastics Recovery’ and ‘Flow Polymers LLC’vii, with the intention of increasing the durability of these biopolymers as well as decreasing production costs, which will allow these more natural bags to compete with the non-biodegradable polyethene bags that currently dominate the market. If global governments were to invest into this R&D, the process would be accelerated and the transition to biopolymers would come sooner. Direct investment may be unrealistic, especially for less environmentally aware nations, so money from an umbrella organisation to which lots of countries contribute to, for example the United Nations, may be a better course of action.

It is worth noting that there is significant inequality in the output of plastic waste into the ocean, China, Indonesia, Philippines, Vietnam and Sri Lanka lead in outputting the most plasticviii. Perhaps unsurprisingly, these countries have little to no enforceable environmental policy regarding safe waste disposal, and it is often the case that countries with the weakest environmental policies and educational infrastructure are least equipped to deal with the consequences. To compensate, more developed countries and umbrella organisations must step up and either impose regulations on the main perpetrators, or ideally begin to remove and dispose of existing plastic pollution. This highlights an important distinction between regulating countries to discrete levels of plastic pollution (ultimately zero) and the removal of existing plastic, which must occur for the effects of previous pollution to be somewhat reversed.

References i https://www.nationalgeographic.org/ encyclopedia/microplastics/ [accessed November 2020] ii https://www.nationalgeographic.com/ environment/habitats/plastic-pollution/ [accessed November 2020] iii https://www.britannica.com/science/ plastic-pollution/ [accessed November 2020] iv https://ourworldindata.org/plastic-pollution [accessed November 2020] v https://www.independent.co.uk/ news/uk/home-news/landfill-sites-coast-spill-sea-erosionpollution-a9338746.html [accessed November 2020] vi https://www.gov.uk/government/news/ worlds-most-remote-island-helps-uk-exceed-protectedocean-target [accessed November 2020] vii https://www.plasticsnewsdirectory. com/category/materials-suppliers/bioplastic-biopolymer [accessed November 2020] viii https://www.worldatlas.com/articles/ countries-putting-the-most-plasticwaste-into-theoceans.html [accessed November 2020] Christopher J. Rhodes (2018) ‘Plastic Pollutions and potential Solutions’, volume 101, issue 3, Science Progress

Photo by OCG Saving The Ocean on Unsplash