If I train for a triathlon or 5k parkrun, how much weight will I lose?

Either I’m really stupid or there seems to be some global myth going around about weight loss.

Some eminent physicist discovered that you can’t just create mass. Mass (weight) and Energy (calories) are tied. E=MC2. (C is the speed of light, incidentally, but don’t think we’ll be running that fast).

Essentially if you burn off more calories throughout the day than you consume then you WILL lose weight. It really is that simple. There is no such thing as “big-boned” or “naturally thin” or whatever: consume less than you burn. And THAT is your lifestyle.

Some people are “naturally thin” because of how little they eat and are active.

If you do wierd stuff like stopping drinking water then your body will compensate by RETAINING water. Just consume stuff naturally.

There will be some bizarre medical conditions out there but they will affect 0.01% of the population so don’t worry about them you almost certainly have not got one, you are most probably normal. Sorry to break that one on you, you’re only special to your friends and family 🙂

So how much weight will I lose?

Sorry I’m still avoiding answering that question.

First challenge your assumptions. Do you really want to lose weight (you shout back “YES of course I do that’s why I’m reading this!”). But let me try again, “Do you want to change your body shape or lose weight”. Pause. You may well find that you could lose 2 inches around your waist and not lose weight. Muscle is more dense than fat.

If you exercise more you get hungry and you probably will have an increased desire to consume more calories as a result (which is a healthy response).

If your calorie intake stays the same and your calorie burn stays broadly similar (no weight change), then exercise will almost certainly start to make your body become more dense and change to a fitter, healthier, stronger shape. I would suggest that you might really want to primarily change your body shape NOT lose weight per se.

Well in that case I’m not going to bother exercising and doing your 5k stuff then. I’ll just go on a diet.

Of course that would be up to you. However consider this. It is surely true that any diet ‘kind of works’ in the sense that diets all expound consuming less calories then you burn. However many diets assume your activity level will not change and so you just eat more temporarily-filling, calorie POOR, foods or just simply pseudo-starve yourself. Fine, as I say, that kind of works. BUT what does your body do in response. Well your body still keeps on burning calories to do the stuff you normally do each day, unfortunately you might find that it consumes the calories stored in your muscles as well as your fat.

Now the inevitable conclusion to a diet is that you stop it and revert to type. You go back and eat more calories. Unfortunately your body does not store these new calories as muscle but rather as fat. So you put on fat. So the net effect of your diet is that you will lose muscle and gain fat. You will have a worse body shape than when you started! That diet WILL MAKE YOU FATTER…eventually. You didn’t really want that did you? Oh and you’ll probably be heavier and more miserable as well.

Diets seem like an easy solution but they aren’t. They fail. Often. Very often. Not always but usually.

What you need is a lifestyle change.

And that will involve a little more exercise. Sorry no magic bullet. You can stop reading this and try and find a mythical magic bullet. Plenty of people will say that one exists. But it doesn’t. Honest, don’t delude yourself.

I would say, however, that 5k runs are the most time effective way of burning calries in a cheap and (relatively!) enjoyable way.

You say, “But all that exercise is going to make me muscley. I don’t want to end up looking like a German shot-putter“.

Are you really planning to THAT much exercise WOW. I am impressed. To put on lots of muscle you have to do a huge amout of anaerobice exercise and consume masses of protein. Running 5k ain’t going to do that to you. Honest. Never. It just won’t. And I mean never, ever. That is to say, it won’t do that, honest. Just believe me. I’m sure. I really really am sure…positive…definately. OK, I admit it may well eventually tone you up like some movie star…but you wouldn’t want that would you!?

Eat healthily: Exercise more. (That sounds terribly unoriginal)

Oh and by the way, genetics permitting, that’s all you need to do to live longer as well. It’s a bit of a no-brainer really.

So to answer the question of how much weight you will lose. The answer will be that it depends on how much exercise you do and how much food you consume. Not the answer you wanted, I know, sorry, but it’s true.

And as a post script: the actual amont of calories you burn doing a single 5k is not that great. Bizarrely the longer it takes you to run the 5k the MORE calories you will consume (as you are exercising for longer). Although it is not quite that simple. Maybe you will burn a few hundred calories and that will translate to a few grammes of weight loss during a single 5k. Hopefully, as you have read this far, you will realise that that is not the point. Just as it is not the point that if you eat 500 calories a day less then you simlarly lose only a trivial amount of weight each day. And further to that post script if you want to exercise effectively to lose weight try to do at least this:

• 1x parkrun a week
• 1-2x run as far as you can a week, slowly, in chunks
• Do weights/pilates

Interesting factette: When you ‘burn fat’, 80% of it is oxidised as comes out as carbon dioxide as you breathe. How do you breathe more? Exercise. Go figure.

Interesting factette (2): You will lose more weight after you have exercised as your body adapts to the exercise you have done and also as you have an increased muscle mass and increased metabolic rate because of that increased muscle mass.

Also I appreciate that super-fit people often scoff at those trying to lose weight. Losing weight is hard for lots of reasons. The key thing is ‘lifestyle change’. Be nice everyone. It’s not easy.