Human Obesity Pandemic: Calorie Requirement of the Whole Population

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Human obesity pandemic is sweeping across the world with an alarming rate – causing disease in its wake (metabolic syndrome, cardiovascular disease, diabetes, etc.) and mowing hundreds of thousands on a daily basis.

In addition, obesity has implications on the health care costs severe enough to hamper world economic growth1;2.

In a paper published just this week, ‘The Weight of Nations: An estimation of adult human biomass’, the authors, Sarah Catherine Walpole et. al. have come out with interesting figures about human fatness!

The results of their study state that because of increasing obesity across the world, there is a need to produce food equivalent to feed half a billion people more as compared to the actual population3.

The Human Population-Food Supply Connection

In 1826, Malthus TR had published an essay stating how the human population would eventually outstrip food production4. During the initial quarter of the 20th century, technological advances, especially in the agricultural field, increased food production; doubts were thus cast over the theory of food running out.

However, the current scenario of increasing population, alarming prevalence rates of overweight and obesity as well as global climatic changes has kindled a new found interest in Malthus’s prediction.

Copying the ‘Animal Species Model’ of Food Requirement

Traditionally, food requirements of human population have always been calculated taking into consideration the number of human beings. However, with increasing number of humans who are overweight or obese, there has been a need to re-evaluate the food requirements according to biomass or actual, total weight of the population.

In ecological studies, the energy requirement of a species is calculated using the number of members of the species and (multiplied by) the average weight of an individual member. Extrapolation of this model to the humans has revealed the staggering fact that we are currently equate to half a billion people more than the number of human beings actually living.

Energy Requirement of the Humans

According to current estimates (2011), more than half a billion adults are overweight5. Furthermore, the body mass of entire populations seems to be increasing across all nations5.

On an average, a human being spends 25-50% of the calories on physical activity while 50-75% is utilized for the metabolic processes in the body3. It is common knowledge that a heavier mass requires more energy to be moved. Increased body mass also concurrently increases metabolically active lean tissue6. Thus, owing to the need to move a heavier biomass and more calories required by increased muscle mass, overweight and obese people would be spending more calories as opposed to their leaner counterparts7. Thus, overweight and obese individuals will require more calories for physical activities and this translates into more food requirements for the population.

Needless to say, this increase in human body mass will likely contribute to increasing the price of food. This is likely to make food harder to come by in the poorer countries. On the other hand, the ready availability of food and purchasing power in the affluent countries will further compound the problem of overweight and obesity.

Discussion

The problem of increasing global human biomass needs to be taken into account when calculating ecological sustainability. It is estimated that although, the largest increase in human population is expected to be in the Asian region, the US will carry most biomass in terms of sheer numbers. Notwithstanding the swelling of US population to 403 million in 20505, much of the increase in food demand will be due to increased biomass rather than increase in the number of people.

All in all, it can safely said that if all the countries were to be ‘as obese as the US population’, the biomass would correspond to an extra billion people. Although, this won’t be strictly true in terms of energy requirement, we’d still be needing food equivalent to calorie requirements of an extra 473 million adults3.

Citations

(1) Freedman DH. How to fix the obesity crisis. Sci Am 2011; 304(2):40-47.

(2) Kypreos KE. Mechanisms of obesity and related pathologies. FEBS J 2009; 276(20):5719.

(3) Walpole S, Prieto-Merino D, Edwards P, Cleland J, Stevens G, Roberts I. The weight of nations: an estimation of adult human biomass. BMC Public Health 2012; 12(1):439.

(4) Malthus TR. An essay on the principle of population: or, A view of its past and present effects on human happiness. London, Reeves and Turner; 1888.

(5) Finucane MM, Stevens GA, Cowan MJ, Danaei G, Lin JK, Paciorek CJ et al. National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 country-years and 9.1 million participants. Lancet 2011; 377(9765):557-567.

(6) Schofield WN. Predicting basal metabolic rate, new standards and review of previous work. Hum Nutr Clin Nutr 1985; 39 Suppl 1:5-41.

(7) Prentice AM, Black AE, Coward WA, Cole TJ. Energy expenditure in overweight and obese adults in affluent societies: an analysis of 319 doubly-labelled water measurements. Eur J Clin Nutr 1996; 50(2):93-97.

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Dr Deepak S Hiwale

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