Have you ever thought which is better? Exercising whilst eating whatever you like OR going on a strict diet only without exercise?

It is obviously a no-brainer that both exercise and diet would be ideal.


Diet vs Exercise

But the interesting question is, which one is better? Diet or exercise? I have patients who just don’t like to exercise and just want to go on a strict diet be it juice fasting, the cabbage soup diet or whatever that Weekly periodicals come up with as the latest fad. I have another group who think that because they are exercising they can eat whatever they fancy!

Well, some researchers at the University of Missouri asked the same question.

So, to answer it, they did a study where they took mice that were genetically prone to obesity and tested them. They had 3 groups. One group was allowed to eat as much as they wanted but kept sedentary so no exercise was allowed. The second group was made to exercise (on a running wheel) and not restricted to the amount of food eaten. The third group was kept on a diet to match the weight loss of the exercising second group and no exercise.  All the groups were given the same type of food.

The findings?

Well, the first group put on the most weight as expected as they had no exercise and allowed to eat any amount of the supplied food.

The third group (restricted amounts of food) lost weight as did the second group (exercise and unrestricted amounts of food).  Blood tests showed that the exercised group was much healthier. They had less inflammatory markers, their insulin resistance improved and their fasting blood sugar levels were lower. The amount of fat around the belly and fat around the aorta (the main artery leading out of the heart) were reduced.  They were also spontaneously more active even when not running on their wheels. So, these mice just moved around more in their cages compared to the other two groups. In other words, they had more energy.

But the most fascinating finding was …

The exercised group developed different gut bacteria than the other groups despite eating the exact same food as the sedentary group with unlimited access.

Remember all these mice in the experiment were genetically prone to obesity.  These mice would become obese on a normal mouse diet. But with exercise alone they lost weight and the microbiome changed.

Generally speaking, the microbiome in the guts of obese mice (same finding in humans) are different to the microbiome in the guts of lean mice (and humans). Exercise suppressed the growth of bacteria that induce obesity and encouraged the growth of bacteria that induce weight loss. What an ally!

So how then do these changed bacteria in the exercised group help you lose weight (and get you healthy)? The answer to this is complicated but in essence, it is due to the Short Chain Fatty Acids.


What are Short Chain Fatty Acids (SCFAs)?

These are products made by the gut microbiome by fermenting the indigestible fibre that we consume.


What do Short Chain Fatty Acids do?

They have several very useful functions including:

  • feeding the cells of the gut lining of the large bowel
  • preventing the development of a leaky gut and so preventing bacteria or undigested food from entering the circulation
  • improving immune function
  • preventing constipation
  • preventing bowel cancer.

But in the context of exercise, SCFAs activate an enzyme called AMPK in muscle tissue that has several functions. It regulates how fat and glucose are used in the muscle. By the efficient use of glucose and fat, AMPK prevents obesity and the development of diabetes. We know that diabetes is a condition where the body is unable to properly manage the sugar (including refined carbs) consumed. But with regular exercise the activated AMPK does its job of burning up the sugar and fats. Without AMPK more fat is deposited in the muscle. You can find out more here.

The other interesting role that SCFAs play is in the gut where they increase the production of a hormone in your body called PYY. This is a satiety hormone so it is responsible for you feeling satisfied after a meal and so signalling to the brain the you don’t need to eat any more. Yet another function of SCFAs in preventing obesity.


How do you increase Short Chain Fatty Acids?

As mentioned above, SCFAs are produced by the fermentation of indigestible carbohydrates. These are the fibre part of carbohydrates that we cannot digest but passed onto the bacteria in the large bowel. The typical Western diet is high in saturated fats and refined carbs and very low in fibre. If you are not getting enough fibre in your diet, your bacteria don’t get fibre, so you don’t produce enough SCFAs and you don’t feel satisfied after a meal, so you eat more and so on.

What foods contain these particular fibres that will allow your bacteria to produce SCFAs?

  • Whole grain cereals
  • onions
  • leeks
  • brown rice
  • barley
  • beans
  • lentils
  • asparagus
  • Jerusalem artichokes

Needless to say, you should not eat any of the above foods if your sensitive or allergic to any of them.

With the experimental mice, the food was balanced i.e. it had the right amount of protein, carbs and fat but the amount consumed varied. With people the amount and quality can vary enormously. We all have different preferences so our diet varies as to the protein, fats and carbs content. Not only that, the food quality varies as well i.e. good fats vs bad fats, refined vs complex carbs etc.

Humans can’t be controlled as easily as mice for experimentation but the message from the mouse study is clear. Exercise on a good diet and you can achieve weight loss and get healthier and have more energy

Exercise on a good diet and your ally, the gut bacteria morph to help you lose weight, improve your health and gain more energy.

Look after your gut microbiome and they look after you.

A win-win for both of you.

Yours in Health
Dr Iggy Soosay