Obesity 1: What is it and what are the impacts?

Obesity is a disease which is causing significant health challenges globally. Not only in the developed world, but also in developing nations. Obesity is defined as excess fat deposits in the body and it can influence a person's physiological health, mental well-being and how they interact with their environment. This article will touch on the scientific mechanisms at play during metabolism and the health impacts that obesity causes. Part 1 of 2 will begin to understand the various conditions that make this a growing global epidemic.

Obesity is defined by a measurement called Body Mass Index (BMI). BMI is a tool used to understand a person's weight proportionally to their height. It is calculated using the formula weight in kg divided by height in meters squared (kg/ m2). 

Defining your BMI

Weight Status	BMI
Underweight	Below 18.5
‘Normal’	18.5-24.9
Overweight	25-29.9
Obese	30 and higher

There are some limitations to this method of labelling an individual's weight status. For example, generally, Asians have a lower BMI compared to other similar stage adults due to their genetic makeup. It is estimated, that Asians with a BMI of 23 or over are at risk of increased health problems.

Additionally, these measurements do not take muscle mass into consideration. This can increase an individual's weight in kg but not affect their fat storage content. Therefore, highly muscular individuals may have a higher BMI and less associated health risks. Additional measurements can be taken to negate these issues such as waist circumference (upwards 102cm in men and 89cm in women are associated with health risks) and body fat percentages. Together, these measurements give a much more accurate representation of a person’s risk of obesity and the risks that are involved with this condition. 

The Stats

Source: WHO (1 March 2024)(1)

• 1 in 8 people in the world are living with obesity

• In 2022, 43% of adults were overweight. About 16% of these are obese. 

• In 1990, 25% of adults were overweight. 

• In 2019, 5 million deaths were attributed to non-communicable diseases, in which, obesity plays a major role in the onset. (2)

The Simple Science

Metabolism

When we eat and digest food and drinks, our body converts these nutrients into energy. This is known as metabolizing. The idea of metabolism is that the amount of energy we consume (energy in / calories) minus the amount of energy we expend (energy out / exercise) equals energy stored (fat). This formula is controlled by our conscious mind and while it is somewhat true, it is too simplistic. 

Negative Feedback

There is also another process at work during metabolism called negative feedback which aims to maintain a stable internal environment in your body. This means that our body understands what we need to survive and will send signals to your brain to control your behaviour (ie. to stop eating). This is controlled by the subconscious mind, therefore, we have little control over this. This subconscious drive is directed by many factors which we will touch on in part two. 

The outdated rhetoric of ‘energy in’ vs ‘energy out’ is a concept that has been disproven time and time again in both research and first-person analogues relating to obesity. We will look closer at the influence of many factors including genetics, epigenetics, environment, geography and how economics can affect the food we eat and how our body responds to these foods. 

What are the health impacts?

Being overweight or obese causes an abundance of health issues. Many of these issues cannot be overtly seen and are called non-communicable diseases. These diseases include: 

• Heart disease

• Stroke 

• Diabetes 

• Cardiovascular disorders 

• Digestive disorders

Excess fat in the body increases inflammation which is a major precipitating factor of these conditions. In the example of heart disease and stroke, extra fat particles are present in the blood stream, causing blockages and adipose tissue buildup on vital organs. Additionally, the heart needs to work harder to push blood around the body when it is under heightened load and pressures, increased blood pressure and cholesterol. This in conjunction with hormonal implications, can cause the onset of non-communicable diseases.

Economic impacts

Not only does obesity have a huge impact on the health of the population, the cost of this disease to society is enormous. It is predicted that the economic impact of obesity will reach $3 trillion US dollars by 2030. While it is difficult to manage, the aim would be to prevent obesity in the population before it reaches treatment stages. 

While obesity was often seen as an issue of high-income countries, it has become apparent that developing nations are seeing a rise in obesity levels. As these populations develop, food consumption may shift from simple cooking methods to processed foods being introduced in the diet for a multitude of reasons. Greater intake of processed foods, generally high in saturated fats and sugars and calorie dense, cause weight gain. These foods often fail to meet vitamin and mineral requirements causing further health consequences such as deteriorating bone health and deficiencies. We see individuals carrying excessive weight, coexisting with malnutrition. This has led to what is called the ‘double- burden’ of malnutrition.

Prevention and Management

In the past obesity was understood to be an output occurring when an individual consumes too many calories and they are not burning off enough through exercise. Therefore, ‘energy-in’ vs ‘energy-out’ is out of balance. When the body is not burning the calories that we give it, it stores these extra calories as fat or carbohydrates. This is an extraordinary evolutionary concept during hunter-gatherer times, to store energy due to the unknown circumstances of one's next meal. However, with an abundance of food available to us at all time in today's world, this is not necessary anymore. Our understanding of obesity has shifted from being a matter of willpower to being a broader societal issues which encompasses genetics, hormonal, environmental, political and social issues.

As one form of treatment, weight management strategies are usually delivered in primary care settings and are developed using the simplistic knowledge of how people store and lose weight. Examples of these interventions might include a meal or exercise plan with the support of a practitioner. Many weight loss plans see individuals lose weight and keep this weight off for 12 months post-intervention, however, the weight loss is generally modest (approx -2.5kg over 12 months) (4, 5, 6). Nonetheless, this is a low cost, prevention strategy which has proven effects. Greater weight loss is seen in individuals who feel supported by their practitioners, highlighting the importance of de-stigmatisation and understanding during weight loss periods. 

However, we have seen time and time again that these weight management strategies are not effective for everyone. As highlighted, there are many more factors at play in this intricate network of chronic disease, and research is beginning to recognise these push-pull factors.

Part two will give you an insight into these intricacies.

References

1. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight

2. GBD 2019 Risk Factor Collaborators. “Global Burden of 87 Risk Factors in 204 Countries and Territories, 1990–2019: a systematic analysis for the global burden of disease study 2019”. Lancet. 2020;396:1223–1249.

3. https://iris.who.int/bitstream/handle/10665/367784/9789240073234-eng.pdf?sequence=1

4. Ahern AL, Wheeler GM, Aveyard P, et al. Extended and standard duration weight-loss programme referrals for adults in primary care (WRAP): a randomised controlled trial. Lancet 2017;389:2214-25. doi:10.1016/S0140-6736(17)30647-5

5.  LeBlanc ES, Patnode CD, Webber EM, Redmond N, Rushkin M, O’Connor EA. Behavioral and Pharmacotherapy Weight Loss Interventions to Prevent Obesity-Related Morbidity and Mortality in Adults: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA 2018;320:1172-91. doi:10.1001/jama.2018.7777

6. Madigan C D, Graham H E, Sturgiss E, Kettle V E, Gokal K, Biddle G et al. Effectiveness of weight management interventions for adults delivered in primary care: systematic review and meta-analysis of randomised controlled trials BMJ 2022; 377 :e069719 doi:10.1136/bmj-2021-069719