Question # 3: What determines how much fat we store? Can Evolution and Genetics both contribute to this?

It seems that storing fat is an evolutionary strength. I have found some interesting snippets about this which I would like to share with you:

In spite of the bad press, stored fat is actually a really wonderful thing. Without the capacity to store energy in the form of fat, we would have been unlikely to survive through millions of years of evolution and we would certainly look very different to the way we look today. We needed the capacity to store energy to survive periods of famine, and fat is a very sensible way to do this.

Excess stored fat is a particularly difficult problem to solve in part because we have evolved such sophisticated processes to protect fat stores once we have them.

One of the best-characterised physiological systems involves leptin, a protein secreted by our fat stores (adipose tissue) – that tells the brain that there is plenty of energy available stored in the form of fat.

As we store more and more fat the leptin level in our blood will increase in proportion to the increase in stored fat. Our brains get used to this higher level of leptin, so administering more leptin over and above this higher level of leptin does not seem to help. Instead, it is when leptin levels fall that leptin becomes a very important signal. When we try to lose weight, there is a disproportionately large fall in circulating leptin in spite of only modest fat loss.

A fall in leptin is an attempt to defend fat stores with leptin functioning as the signal to the brain in a negative feedback loop that maintains the stability of fat mass. A fall in leptin is associated with increased sensations of hunger and an increase in “reward-related” behaviours.

Reduced leptin is also a trigger for depressive symptoms in animals. So, when we try to lose weight, our fat tissue sends signals to the brain to try to resist any further loss of fat; we feel hungry, we seek rewards, and we might feel a little down or depressed.

Dylan Thomson, University of Bath,

A question I get often is also – is it in your genetics? Does it mean no matter what you do, you can not really influence the shape of your body? Unfortunately, it is true that your genetics can play a role in how much fat you do or don’t store.

  • Inherited metabolic disorders, where certain enzymes in the body are not present or not functioning, require medical intervention and are present from birth.

When is genetics a significant contributor?

  • Genes are probably a significant contributor to your obesity if you have most or all of the following characteristics:
  • You have been overweight for much of your life.
  • One or both of your parents or several other blood relatives are significantly overweight. If both of your parents have obesity, your likelihood of developing obesity is as high as 80%.
  • You can’t lose weight even when you increase your physical activity and stick to a low-calorie diet for many months.

When is genetics a low contributor?

  • Genes are probably a lower contributor for you if you have most or all of the following characteristics:
  • You are strongly influenced by the availability of food.
  • You are moderately overweight, but you can lose weight when you follow a reasonable diet and exercise program.
  • You regain lost weight during the holiday season, after changing your eating or exercise habits, or at times when you experience psychological or social problems.
  • These circumstances suggest that you have a genetic predisposition to be heavy, but it’s not so great that you can’t overcome it with some effort.


Does this mean that your fitness journey is futile and you may as well go back to living on the couch with snacks?

Absolutely not!

Does it mean it might be harder and you will need to train smarter?

Yes, most likely! But it will be worth it!

My next tip will deal with strategies for how we can overcome these challenges. Watch this space!

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