Obesity: A 20th Century Disease

Science of Food Nutrition and Health

Vinod Puri

(Publishers: Austin Macauley Publishers, London, 2023)

Obesity: A 20th Century Disease

The World Health Organisation (WHO) in 1995 acknowledged that obesity and overweight are potential health hazards and represent a rapidly growing threat to the health of the world population.  The American Medical Association (AMA) further endorsed the findings of WHO and designated obesity a disease in 2013.

The major cause of obesity is attributed to the overabundance of easily accessible foods because of agricultural and technological advances in the last 50 years coupled with a sedentary lifestyle. A large body of evidence suggests that there is a direct association of obesity with hypertension and stroke, cardiovascular diseases, diabetes, osteoarthritis, certain types of cancer, and pulmonary diseases.

It has been recognised that Obesity is not limited to developed nations but has spread globally. An expert panel report by WHO estimated that there were over 1 billion adults who were obese or overweight representing 35% of the total world population. WHO further reported that if the current trends continue unabated the prevalence of overweight and obesity could reach 50% of the adult population by the year 2030.

 

During the evolutionary history of mankind, hunting and gathering for food was the key and important activity.  The major cause of disease was attributed to famine along with pestilence. Scientists believe that the genetics of humans adapted to the mechanism of storing their food as fats when supply was abundant, and these food reserves contributed to the survival of the human species during an extremely harsh and demanding environment. The deposition of fats is an adaptive physiological process of energy storage. However, the process turned maladaptive when the balance between food consumption and energy expenditure changed because of the Industrial Revolution ensuring an abundance and continuous food supply and becoming a major factor influencing overweight and obesity.

 

Obesity is not new to mankind.  The historical records of figurines found in Spain dating back to 25, 000 BC of ‘Venus of Wilendorf ’reveal a faceless woman with voluptuous breasts, a rotund abdomen, and large curvaceous thighs. It is believed that such women who existed at that time represented an object of desire and worship and a fertility symbol. Obesity was then considered the privilege of the upper class. However, the role of obesity as an impediment to health was recognised by Hippocrates in Greece as well as Egyptian and Indian scholars.

 

WHO defines overweight and obesity as abnormal or excessive fat accumulation which can be qualitatively determined by dividing a person’s weight in kilograms by the square of height in meters represented as Body Mass Index (BMI).  BMI is a crude but easy and cost-effective method to determine an individual’s body weight across populations. BMI has been used to classify people into different categories:

·         BMI <18.5 – Underweight

·         BMI 18.5-24.9 – Normal

·         BMI 25-29.9 – Overweight, and

·         BMI >30 – Obese.


Overweight and obese individuals (BMI >25) are considered to have a major risk for diet-related chronic diseases.

 

The factors that contribute to overweight and obesity include:

  • Positive Energy balance between the calories consumed and calories expended. The relationship between higher energy intake and gain in weight is not linear because of physiological control that dictates the net absorption of nutrients. However, continuous increases in energy intake and decreases in physical activity are the key factors in gaining body weight over longer periods.
  • Genes have also been implicated to play an important role however, their effect is rather small. Some genes have been identified that are associated with obesity.
  • Lifestyle and individual behaviour have also been positively linked with weight gain and obesity. Researchers have identified that in addition to diet quality and diet patterns, an individual’s lifestyle, sleep patterns, and physical activity positively contribute to obesity.
  • The Agricultural and Industrial Revolution ensured food security and changed the composition of the foods that we consume. Our ancestors relied on foods that were rich in proteins and low in carbohydrates and were involved in intensive physical activity.  The modern diet is rich in carbohydrates, protein, and fibre and also includes substantial amounts of trans fats, refined grain products, and refined sugar resulting in a higher intake of calories.
  • Physical environments such as urban sprawl provide easy access to highly processed energy-dense foods which along with reduced physical activity, and increased television and computer time is contributing to overweight and obesity.
  • Socioeconomic factors such as income, education, and employment status may also be linked to obesity. Low-income groups tend to consume low-cost unhealthy food compared to high-quality nutritious foods supporting obesity.
  • Urbanisation and Globalization are other key factors in the global rise in obesity. Trade liberalisation facilitated the introduction of highly processed low-cost foods that are rich in sugar and fats. The infiltration of fast foods such as McDonald's, KFC, Coca-Cola, Pepsi, etc. into low and middle-income countries is shifting the balance of diet patterns toward Western countries. Globalisation, no doubt has improved the quality of life in developing nations by reducing poverty, hunger, and infectious diseases, but on the other hand, contributed to increasing the rates of obesity and associated non-communicable chronic diseases.

Regardless of the factors discussed above numerous studies indicated that unhealthy diet patterns, lack of physical activity, and genetic disposition are responsible for weight gain and obesity. The pathogenesis of obesity is rather complex; however, all the studies point out that an imbalance between energy intake and expenditure is the root cause of the global obesity epidemic.

 

Being overweight and obesity are also closely associated with many health risks which I will discuss in a separate blog.

 

For further details refer to Chapter 10 in my book on the Science of Food Nutrition and Health.


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