November 23, 2017

Why He’s Fat, She’s Slim And The Rest Stay Curvy

Obesity1

As the old saying goes, one man’s meat is another man’s poison. Traditionally African’s are known to attribute affluence to body size; the bigger the better. This phenomenon is not peculiar to Africa though. Up until the 19th century, the west had also attributed obesity to wealth and high social standing. These attitudes begun to change in the early 19th century and slimness gradually became the desired body shape.

As the prevalence of diseases such as diabetes, stroke and hypertension start creeping up we are now more health conscious and today’s generation strive to maintain a healthy body weight. The health implications of obesity is however not a modern day phenomenon. Ancient Greek physicians are credited for being the first to recognise obesity as a medical disorder and associated irregular menses and infertility to obesity. Hippocrates famously quoted that “sudden death is more common in those who are naturally fat than in the lean”

Today, more often than not, you now hear questions like;

  • How do you manage to stay so skinny with all the food you eat?
  • How did you have twins and still maintain your weight?
  • Are you on a diet or do you go to the gym?

 

But to what extent can one really influence their body shape? Like nature versus nurture what if science told you there’s not much you can do about your body metabolism and shape. Evidence from historic artefacts suggests obesity has always been prevalent in society. A historic figurine known as “Venus of Willendorf” which depicts an obese female torso is one of such historic suggestions of the human race been no stranger to obesity.

Obesity2

To eat or not to eat……

Fact: We eat to grow. Which means the more you eat the more you put on. But it is not always so straightforward. Indeed weight gain comes from excess fat, but this is not only dependent on how much you eat but also how your body processes what you eat.

The desire to eat is often triggered by the sight of food or the rumblings of the stomach both of which is controlled by the hypothalamus in the brain. A hunger hormone known as Ghrelin is released by the stomach when the body’s energy is low which explains the stomach rumblings. The release of ghrelin notifies the hypothalamus of the body’s hunger and the brain triggers the release of another hunger stimulating hormone known as neuropeptide Y. By this point, your mouth is probably watering from the sight of that bowl of soup and if there’s no food in sight your tolerance level for other people has probably dropped and woe to the victim who steps on your toes.

After eating, another hormone which acts as an appetite suppressant known as leptin is secreted by the body’s fat cells to notify the body of your satisfaction and full state.  As food is ingested, the level of leptin begins to rise and peaks when the body is full at which point you’re feeling friendly again.

Ghrelin makes you hungry, Leptin suppresses hunger. A defect in leptin = keep eating = get fat

 

Leptin and the Ob gene.

There is strong scientific evidence suggesting that leptin coupled with the obese (Ob) gene is the key player in regulating body weight and the subsequent cause of obesity. Mutation in the Ob gene leads to a defect in its function which primarily involves the secretion of leptin. This defect leads to increased food intake and decreased physical activity causing obesity.

In an experiment where mice were deprived of leptin as a result of a defective Ob gene, they were observed to develop severe obesity caused by increased food intake and reduced energy usage. These mice also developed other health conditions including infertility. When these mice were then injected with leptin, the aforementioned effects were reversed and they consumed less food, increased energy use and regained fertility.

In a similar experiment in humans, children suffering from childhood obesity due to a defect in their ob gene were treated with leptin in a procedure known as leptin replacement therapy over several months and were observed to have lost their fat mass over time as a result of reduced food intake and subsequent reduction in calorie intake.

Obesity3

Whiles there is no doubt that current trends in lifestyle has influenced the increasing obesity burden worldwide there is growing scientific evidence linking genetic defects and malfunctions in the brain to obesity. It is for this reason that some individuals are prone to severe obesity no matter what they try to do to stay in shape and why some children suffer with severe obesity from a young age.

So next time you wonder why He’s Fat, She’s Slim and the rest stay curvy, think ‘leptin’, genetics and that slice of cake.

References

Friedman, Jeffrey M., and Jeffrey L. Halaas. “Leptin and the regulation of body weight in mammals.” Nature 395.6704 (1998): 763-770.

Farooqi, I. Sadaf, et al. “Beneficial effects of leptin on obesity, T cell hyporesponsiveness, and neuroendocrine/metabolic dysfunction of human congenital leptin deficiency.” The Journal of clinical investigation 110.110 (8) (2002): 1093-1103.

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