Why exercise cannot compensate for a bad diet

Many of us believe that as long as we burn calories through exercise it doesn’t matter what we eat. We might even hold the belief that the food we eat burns off into ether. As a side point, we can assume that we excrete our body fat as carbon dioxide (CO2) through our breath and water (H2O) through sweat, urine and breath.

The conventional wisdom on weight gain

The popular belief of eating what we want as long as we exercise comes from the energy balance hypothesis, popularised since the 50’s. In other words, to achieve weight loss we need to eat less and move more. This hypothesis lead to the view point that a high fat diet will lead to weight gain. This is because 1g of fat has 9 calories while 1g of protein or carbohydrate has 4 calories. So if we eat, let’s say, cheese we need to exercise harder to be able to burn off the calories.

The endocrinological hypothesis or the carbohydrate insulin model

Even to this day, there is a lot of debate around the validity of the energy balance hypothesis. What is fuelling this debate is the fact that this hypothesis was the backbone of all health policies that were develop to control obesity. However, for the last 30 years, the obesity rates have soared. Before World War 2 there was a second hypothesis that emerged.

With the discovery of the hormone insulin in 1921, the point of view that this hormone is the reason behind our body is accumulating fat. Insulin is the primary hormone excreted when we eat carbohydrates. In simpler terms, when we eat fast releasing high glycemic load carbohydrates (like potatoes, white bread, white pasta, white rice) our body releases insulin. this helps transport the digested carbohydrate to cells to use if for energy or to store as fat (when we have more glucose than we need). This lead to the view point that a low carbohydrate diet will help us control the weight gain.

A new clinical trial has showed that the quality of calories we consume are more important than the quantity, challenging the energy balance hypothesis that all calories are alike. This study doesn’t demonstrate the endocrinological hypothesis. However, it does demonstrate that the old wisdom around calories in, calories out can be challenged and might not be the full answer.

So will exercise help in loss weight?

The simplest answer is: it depends.

If you lower the calorie intake (eat less) and exercise you will experience weight loss. However, this will be short lived because starving yourself is not sustainable. Therefore, the weight loss will not be long term. Also, because of the body’s complex hormonal mechanism as explained in the endocrinological hypothesis the metabolism will start to slow down. And when you return to the normal eating patterns the body fat will be even more difficult to get rid off.

If you don’t change your diet, it will be difficult to lose weight. I am not talking here about a couple of slices of cheese now and then, I am talking about fry ups in the morning, sandwich and crisps for lunch , 2-3 cans of coke throughout the day and finally ending your day with a curry and a glass of wine.

The way you digest a can of coke is completely different to the way you digest let’s say broccoli.

How does the body use Coke?

Assuming you have 3 can a coke of day, these mount to 420 calories which are all provided by sugar. There are around 20 teaspoons of sugar you need to burn off. Half of the sugar is glucose which the body sees as fast releasing carb. Your blood sugar spikes, your body demands insulin to start to send this sugar to different parts of the body. Whatever the body doesn’t need immediately (which is likely since we are sitting down most of the time) is sent as storage. Long term this is transformed into fat (especially belly fat, but not only) which will lead to inflammation.

The other half is fructose. This goes straight to the liver to convert into fat, increasing the release of insulin on one hand and leading to fatty liver on the other.

Finally, insulin spikes blocks leptin, the appetite-control hormon. The brain doesn’t receive the message of “I am full” so it continues to ask for more food, making you hungry. Very likely you will want starchy, “filling” food or a coffee.

You might say “How about Diet Coke or Coke Zero? That has 0 calories”. Yes, it has 0 calories but your body perceives the sweetener as glucose and will still raise insulin and you still end up gaining fat.

How does the body use broccoli?

The same calories (420) are in a head of broccoli (when removing the stalk). Broccoli however contains very little fast releasing carb and also fibre which helps release energy slowly. In effect, this will keep you feeling fuller for longer. With broccoli you don’t have the blood sugar spikes, the insulin resistance and therefore  very unlikely to get the fat and inflammation because the amount of extra glucose will be minimal and eating 1 head of broccoli is just a bit more difficult.

In addition, you are very likely that your stomach will feel full which will send appropriate signals to the brain.

Lastly, broccoli contains vitamins (C, folate) and special compounds. Vitamins are involved in every single bodily process (ie. improved digestion, effective energy production). Glucosinolates help detoxify and flavonoids are anti inflammatory.

In summary, long term wellbeing is achieved by ensuring you are eating a better diet and you use exercise not as a tool to lose weight but for it’s other important properties.