The truth about fat loss

Woman's feet on scales which says 'help'

Most of us have tried to lose weight at one time or another. And we all know the frustrations of the bad days, the highs of the good days and, hopefully, that brilliant moment we weigh ourselves and we’ve done it. The scales are suddenly our friend.

Woman's feet on scales with the word 'help' in the readerBut in amongst all that euphoria, did you ever stop to wonder – what actually happened to all that fat?

Here’s an example of a common scenario.

Jane gets on the scales and decides she wants to lose weight. So she takes more exercise, eats a little less and at the end of six months of living her new, healthier lifestyle she’s pleased that she’s lost a stone. She’s treated herself to new smaller clothes and feels good.

Jane has lost about a stone of fat. How? Where did that fat go?!

The three most common answers I’ve heard are:

  • Was it converted into muscle? No. If that was the case Jane would still weigh the same.
  • Is it excreted? No. The digestive system is completely separate from your metabolism.
  • Did it disappear into thin air? No!

As a personal trainer I come across an awful lot of fad diets and misleading advice. I like to educate people so they understand how their bodies work – which means it’s easier to make decisions on what to eat.

And I think you’ll probably be surprised when I tell you a large amount of that stone of weight was lost by breathing out.

As they say in the shampoo advert… here comes the science.

  • A pound of human fat contains about 3,500 calories, about the same calorific density as coal.
  • Lipids are the main component (87%) and come in a variety of different structures, but what they have in common is that they’re all made up of carbon, hydrogen and oxygen atoms in the approximate ratio of 50 Carbon : 100 Hydrogen : 6 Oxygen.
  • These fat stores are broken down via complex biochemical reactions. This is what we usually call ‘burning calories’. When we work out, or just sit on the sofa keeping our organs ticking over we use these energy stores.
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Fuel burning, fat burning

We know that burning fuel produces carbon dioxide which contributes to global warming. Interestingly, human respiration and fuel combustion have the same end products – we breathe out carbon dioxide and water – but the processes that create this are very different.

Humans are much more complex and need vitamins and minerals in order for this reaction to take place.

One more bit of chemistry… the law of conservation of mass states that during any chemical reaction the total mass of the reactants must be equal to the mass of the products. What does this mean? Well, essentially, the number of carbon, hydrogen and oxygen atoms is the same before and after the fat is burned.

So, the stone in weight is lost predominantly via carbon dioxide being breathed out through the mouth and water loss (going to the toilet, sweating, breathing out moisture etc).

Every year we breathe out about 600 pounds of carbon dioxide, just with day-to-day activities.

When you’re enjoying your favourite exercise (maybe Nordic Walking up a hill?) remember this: you’re breathing in oxygen to metabolise the fat (and glycogen stores) and breathing out to release the carbon dioxide from their metabolism.

So next time you see an advert that promises you that their product will melt fat away, you now know better… all you need to do is breathe.

10 top tips for weight loss

  • Exercise is not just for calorie burn. It’s just as important as a stress release and distraction from potential comfort eating. Plus, it also releases feel-good chemicals serotonin, endorphins and dopamine, which put you in a better frame of mind to make changes to your eating habits.
  • Halve the calories by halving your portion size (or share with a friend).
  • Drink plenty of water. You’ll know you’re getting enough if your urine is pale yellow.
  • Make your own meals, as you’ll probably use healthier ingredients. Adding herbs and spices helps, too.
  • Choose foods that are filling, i.e. that contain fibre and/or water, leafy vegetables, pulses, nuts, soups and salads.
  • Start your day with a protein-packed breakfast – such as eggs with spinach leaves and cherry tomatoes.
  • Get some sunlight in the daytime – it sets your circadian rhythm (body clock), which means you sleep better and are less likely to comfort eat due to tiredness.
  • Distract yourself when you’re hungry with a hobby or game, or maybe call a friend for a chat.
  • Exercise in a group or with a friend – the time passes much quicker.
  • Join a Nordic Walking group. Nordic Walking burns up to 40% more calories than ordinary walking. The effort is spread over your whole body so it feels easier, particularly when going uphill. You burn as many calories as if you were jogging, but without the discomfort.
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Find out more…

Midlands Nordic Walking classes.

The law of conservation of mass, or principle of mass conservation.

About Catherine Hughes

I'm a scientist and after a career in pharmaceuticals, I switched to prescribing exercise as a medicine. I'm a personal trainer, Nordic Walking instructor and co-founder of British Nordic Walking CIC, and British Orienteering coach of the year. I believe there's an exercise for everyone to help them feel healthier or fitter.