Why You Cant Out Exercise A Bad Diet

The general understanding of calories in/calories out for weight maintenance/loss goes like this – we think we can eat horrible food then go for an extra run or hit the gym hard for a few sessions to work off or burn the difference in calorie expenditure. Ta da…easy peasy…

But here’s the thing and here’s why that doesn’t work. Exercise is not that useful for losing weight…yes I just said that, so let me explain….

Everyday we expend energy in 3 main ways:

  • basal metabolic rate (BMR)
  • physical activity and movement, which includes NEAT (non-exercise activity thermogenesis, energy used sitting there jiggling your leg, twiddling your thumbs), and
  • thermic effect of food

Another way is adaptive thermogenesis; when you are cold, your body will shiver to warm you up, or if you decide to go crazy on the M&M’s one night, your body recognises there is a huge availability of additional calories/energy so your body speeds up in response to that. But it only does this acutely/short term. So it’s not like you can sit there and smash M&M’s every week and think you’ll be alright because the body can’t continue to burn off all those additional calories.

What’s interesting out of all of that is that the major player in our daily energy expenditure (DEE) is our BMR, about 60% and what we need to understand is, exactly what that is…

“BMR is the energy cost of our body to keep us alive on a day to day basis. It has nothing to do with physical activity levels, or digestion, it is literally just the energy you need on a daily basis to survive.”

Think of it like this, if you were to go out to your car, turn the engine on and leave it running for 24 hours but didn’t drive it anywhere, you would find that when you came back the fuel gauge would have gone down. That’s because, even though you haven’t driven anywhere, the engine is running, it is still expending energy, and that’s BMR.

So BMR is the minimum energy cost to keep us alive, it has absolutely nothing to do with movement, and this is the number one way in which we expend energy daily.

Now it is true, exercise does influence our metabolic rate, if you were to go and do resistance training and build lean muscle tissue, this will positively influence your BMR. Muscle tissue has a reasonably high energy cost/requirement, much more than fat, so it makes sense to go and do exercise, because the fitter you are, the more adaptations happening inside your body will require more energy. To get fit and to get strong makes sense from a BMR perspective, you will improve BMR.

Physical activity levels, dependant on whether you are sedentary or very physically active, there is an energy cost of about 20-30% of DEE. You want to maximise that by being as physically active as much as possible, and by incorporating NEAT into your DEE plan. How can you do this? A standing work station; when you stand up, you burn much more energy than when you are sitting down. So it makes sense to be standing rather than sitting for really long periods of time.

Thermic effect of food uses about 10-15% of our DEE. It is influenced, or best maximised by eating an unprocessed diet. When you eat food that is processed, that is, essentially doing some of the digestion for you, so your body has to work less hard to free up all the energy from the food. Then it makes sense to try and eat food that is as untouched as possible so your body hard to work as hard as possible to free up all of the energy from the food.bad-diet

In terms of being out exercise a bad diet; considering most of our daily energy expenditure comes from our BMR and not physical activity, it’s going to be really difficult if you are eating a really bad diet to then out exercise it. You would need to start looking at exercising large volumes like 3, 4, 5 hours of exercise a day. You need to become an elite athlete.

The real kicker; the fitter you get the more exercise you need to do because the body adapts and gets more efficient, so you need to keep pushing yourself, you need to lift more weight, do a longer session or going faster and harder. So it’s really quite difficult to expend that much energy from eating a crappy diet.

If you want to exercise for a full time job, like an elite athlete, you could potentially get away with eating a less than desirable diet. But remember that less than desirable diet is having a whole range of physiological consequences on your body; it influences the effect of hormones, contributes to the build-up of plaques, as in atherosclerosis, disordered blood lipids, increased blood pressure etc.…so there are lots of other things going on by eating bad food, not just the notion of weight loss and weight gain.

So, at the end of the day, our DEE comes in 3 ways, the greatest being BMR. Don’t do exercise for purely a weight loss perspective by trying to increase your calorie expenditure, do it from the perspective of increasing BMR, improving hormone sensitivity, reducing inflammation, overall improving body composition and improving your cardiovascular health.

Forget the calorie theory of weight loss (eat less, move more). Do not think for a minute that you can eat crappy food and work it off in the gym.

Claire xo

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