07 July 2011

Why men get fat

Contrary to popular belief, weight gain (and a need to shake the kilos off) isn't merely restricted to the female of the species. DietDoc takes a look at this phenomenon in men.


Dieting to lose weight is often regarded as a female pursuit and men in general, particularly those of previous generations, were not really interested in why they gain or lose weight.

However, modern men are much more interested in preserving their figures and being svelte and fit. So at the risk of being branded sexist, it may be a good idea to consider what factors contribute to weight gain in men and what can be done about this problem.

The basics
Most men have a number of advantages over their female counterparts when it comes to basic physiology and gaining weight. The following factors 'protect' the males of our species against gaining weight:

  • Higher basic metabolic rate (i.e. the amount of energy required to keep the body functioning when at rest, or energy used for physiological processes like breathing, digestion etc.). The male basic metabolic rate is 5% to 10% higher than in women of the same weight and height. The higher basic metabolic rate is attributed to differences in body size and body composition (see next point).
  • Lower body fat percentage compared to women. The average man has a greater proportion of muscle tissue than the average woman and 50% less body fat. The average man has14% body fat compared to 24% in the average woman.
  • Higher maximum oxygen consumption or VO2 max than women, because of the above mentioned higher lean muscle mass and lower body fat percentage.
  • The presence of testosterone, the male hormone, that acts as an anabolic agent to promote increased muscle mass.

In view of these positive factors, it would seem that men are actually 'protected' against gaining weight thanks to their physiology. But men do gain weight and 31% or more of men in South Africa were reported to be overweight or obese by the Demographic and Health Survey published in 1998.

Reasons for gaining weight
The reasons why men gain weight are similar to those listed for women and include the following:

a) Increased energy intake
Ingesting more energy (calories of kilojoules) than required to maintain a man's basic metabolic rate and physical activity will result in weight gain. According to international tables, adult men require approximately 2900 cal or 12200 kJ per day to sustain their energy requirements.

If a man ingests more than his recommended energy allowance on a daily basis (usually due to poor eating or drinking habits), this excess energy will be stored in the body in the form of fat which, over time, will cause overweight and obesity.

b) Decreased energy expenditure
Modern humans are doing less and less physical activity. This also applies to men.

If you take into account that men were 'designed' to be physically strong and participate in strenuous physical activity since the dawn of time, then it is understandable that the modern world with its vast array of time- and labour-saving devices, automated transport and sedentary lifestyles, has reduced the amount of physical activity most men do to a fraction of what was once the norm.

When I was at Stellenbosch University doing my M.Sc. degree, I did a most interesting study with a group of first-team rugby players.

I determined both their energy intakes and energy expenditures for two periods of varying physical activity – during their intensive training and playing season and during the off-season.

These highly active, healthy, young men consumed such large amounts of energy that I often had to check the calculations just to make sure that their total energy intakes of 18000 kJ or more during the training and playing season were correct.

What I did find, is that the rugby players did not reduce their energy intakes during the off-season when they were not training or playing for many hours a day. In other words, these young men were still consuming 18000 kJ or more a day during the period when they were no longer intensely active.

The results showed significant increases in their weights and cholesterol levels. This phenomenon is often observed in athletes when they stop active participation in sport. An example is boxers who gain large amounts of weight when they hang up their gloves.

I think that this type of scenario is a lot more common than we think. Most boys participate in some form of sport when at school and for a few years thereafter. Then the demands of work dictate that these formerly active individuals become sedentary. They often don't have the time or energy to participate in any form of physical activity.

These guys do not think of reducing their habitual energy intake and, as a result, the kilograms pile on until the erstwhile Adonis is overweight and unfit.

c) The question of alcohol
Men are more inclined to join their mates for a drink or two or three after work, and statistics obtained from the Demographic and Health Survey published in 1998 show that up to 50% of men consume alcohol compared to 17% of females.

Alcohol is highly energy-dense, second only to fat, and 1 gram of alcohol will provide 29 kJ. Excessive intakes of alcohol boost energy intakes and can directly cause obesity. One of the fastest ways of losing weight is to reduce alcohol intake and most men can slim down just by changing to soda without the whiskey.

d) Other factors
Stress and depression are often associated with weight gain. Men, despite their generally more relaxed outlook on life, can be just as prone to stress or depression as women. Medications used to treat such conditions can also be associated with weight gain, e.g. some antidepressants and anxiolytics list weight gain as a side-effect.

Men living alone may also be more prone to gaining weight because they do not eat regular meals or have to rely on fast foods and take-aways to provide their daily food intake. These foods are often highly refined and rich in fat.

In view of the above, it is evident that modern men are also vulnerable to weight gain and that men in general should actively combat this tendency. – (Dr Ingrid van Heerden, DietDoc)

(References: Krause's Food, Nutrition and Diet Therapy, Edited by LK Mahan and S Escott-Stump (2000). WB Saunders Co, Philadelphia, USA; Noakes T (1991). Lore of Running. Oxford University Press, Cape Town; Van Heerden, IV, Parry, CDH (2001). If you drink alcohol, drink sensibly. SA Journal of Clinical Nutrition, Vol 14, No 3, S71-S77; Zammit, IV (1969). A Study of the Relationship Between Exercise, Dietary Factors & Blood Cholesterol Levels in a Group of Active Young Men. M.Sc Thesis, University of Stellenbosch).

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