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Weight gain- Not just Calories and Sedentary Lifestyle

The world has more fat people today than any other time in history and the number is increasing.

Worldwide obesity has more than doubled since 1980. There are over 1.5 billion adults who are overweight. Of these over 200 million men and nearly 300 million women are obese. Approximately 43 million of children under age of 5 are obese.

Overweight adults and children are traumatised as the society stigmatizes them as chubby, plump and fat.

The media’s emphasis on skinny models, TV presenters, and celebrities does not help the situation because this implies that plus-size people are to blame for their plight.

But,  what causes obesity?

The fundamental cause of obesity and overweight is an energy imbalance between energy consumed and energy expended.

The two blamed causes are; an increased intake of energy-dense foods that are high in fat, and sugars but low in vitamins, minerals and other micronutrients; and a decrease in physical activity due to the increasingly sedentary nature of modern lifestyle.

However I feel that some overweight people are unfairly blamed for being lazy, not exercising enough and eating junk food. There are other reasons for adding weight which are beyond their control.

What is Obesity and overweight?

Before exploring other factors that cause increase in body mass, let us look at what are overweight and obesity and their unwanted effects.

According to World Health Organisation (WHO), ‘Overweight and obesity are abnormal or excessive fat accumulation that may impair health’.

Body mass index (BMI) is the simplest parameter that is used to measure overweight and obesity in adults.

BMI is defined as a person’s weight in kilograms (kg) divided by the square of height in meters (m). Therefore the units for BMI are kg/m2.

Generally, a BMI greater than or equal to 25 is overweight while a BMI greater than or equal to 30 is obesity. These values should be considered as a rough guide as there are different levels of fatness.

Why is overweight and obesity bad?

High BMI is a major risk factor for several modern diseases such as cardiovascular diseases (mainly heart disease and stroke), diabetes and some cancers (endometrial, breast, and colon).

Overweight and obesity are the fifth leading risk for deaths globally. At least 2.8 million adults die each year as a result of being overweight or obese.

The ‘Big two’

The energy imbalance that is blamed for obesity is based on the first law of thermodynamics.

The first law of thermodynamics, popularly known as law of conservation of energy states that ‘energy can neither be created nor destroyed, but can be transformed from one form to another’.

According to this law, if you drink half litre of beer, the body has two options. The first option is either to use all of it or pass all of it out. The second option is pass some quantity and the remainder is used by the body. All foods follow the same chain, a portion is used in the body, and another share is converted into fat or expelled.

The law of conservation of energy dictates that the energy equation has to balance; the energy consumed in form of food has to be equal to what is used up in the body plus the expelled waste.

According to the law of energy, the weight gain is only blamed on the ‘big two’. Firstly, eating excess calories and secondly lack of physical exercise to convert the excess calories into some other form of energy.

Ideally men should take approximately 2500 Kilocalories while women take 2000 Kilocalories per day. Excess calories above these quantities has to be expelled, otherwise they will be deposited as fat and manifest as overweight.

However the first law of thermodynamics does not tell us how other factors in the body such as gene, gender, age, and ethnicity affect the energy balance equation.

For example, law of energy does not tell us why women deposit fat in different parts of the body from men.

Also, this law is numb on why some ethnic groups such as those with Indians ancestry tend to be prone to weight problems than others.

The energy balance school of thought ignores many other factors which could also be responsible for increasing waste lines.

No doubt that excess calories and lack of physical exercise are the salient factors that contribute to human weight gain. However, the evidence to their contributory role is circumstantial.

For example, those two factors cannot also explain why those who take psychotropic medications such as antidepressants and mood stabilizers or even steroid hormones and contraceptives gain weight. This is despite the fact that most of these medications are calorie free.

Majority of those who follow regular exercise and control calorie intake lose weight. However, others watch their calories and engage in physical exercise, but feel helpless and sometimes guilty when they find themselves piling on kilos.

The  less traveled road

There must be other factors that contribute to this quandary of weight gain than just excess calories and reduced physical exercise.

Let us take the less travelled road and look at some unacknowledged factors that are leading to increased population of overweight people world wide.

The evidence among these factors could also be circumstantial but there is strong scientific evidence to link them to overall increase in weight gain around the world overtime.

  1. Maternal age

Surprisingly, a risk factor to obesity is having an elderly mother.

Generally, the age of mothers before having the first baby is increasing globally. This is necessitated by need to advance in education and career before taking up the role of motherhood.

In early 70s and 80s most women became first time mothers at early 20s. Now that age is increasing and majority are not having babies until late 30s.

Babies born by mothers at such advanced ages are at higher risk of becoming obese.

In Britain, a study of girls aged 9-10 years old found that odds of obesity increased by 14 percent for every 5 year increment in their mother’s age.

  1. Body weight associated with greater reproductive fitness

According to natural selection, physically endowed women are associated with fertility and health-child bearing. Consequently, the number of offsprings is directly related to body weight in women.

BMI (or adiposity) has a heritable component of approximately 65% which is well supported by studies. This suggests that obese mothers can pass overweight genes to their children leading to a higher population of overweight people.

It is also true that leanness to certain point impairs women fertility. This limits their ability to bear children and transfer genes of fineness.

Read the other factors in the next article.

I wrote this article for Kenya’s leading newspaper, Daily Nation on 8th November 2011. You can read it online here. 

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