Calorie counting has taken over from discussing the weather as the national pastime. We focus on how many calories are in foods, not just per serving but compared to other foods. Avocado compete with oranges and apple sauce with butter. Exercise is ranked similarly – which exercise burns the most calories per minute (without worrying about how long it could be sustained)? There are even demands for food labelling to include how much and which exercise would be needed to burn the contents. All of this obsession comes from the mantra ‘calories in vs calories out’. Is it really so simple?

How many calories do we need?

You will often hear the term ‘energy drink’ but energy here is usually indicating that the drink has a stimulant included, not that it is full of calories. The word ‘calorie’ come from ‘calor’ meaning ‘heat’ and is defined as the amount of energy required to raise the temperature of 1 gram of water by 1 degree centigrade. There are 4 calories per gram of protein, 4 in carbohydrates and 9 in fat.

Without worrying too much where the calories come from for now, how many calories should we be consuming? 

To maintain constant bodyweight (ignoring minor fluctuations), your calorie intake should match the expenditure. These are your ‘maintenance calories’. Just existing consumes 60% of your calorie expenditure. This is called NEAT (non-exercise activity thermogenesis) and is highly variable.

There are plenty of convoluted formulas that will predict this based on your weight, height, gender, age, body composition, activity levels, wind direction, solar activity etc. 

You can throw as many details at the guess as you like, but it’s just an estimate, so the simpler the better. Given bodyweight alone is responsible for 80% of the variance, I focus on that and use

Bodyweight (KG) x 31 = Maintenance calories

You’ll often hear people saying how muscle burns more calories than fat. Although true, each kilo of muscle only burns an extra 13 calories a day, so even a lot of muscle will not make a significant difference to your metabolism if your bodyweight were to stay the same. Whenever there is a massive difference in body composition, the impact of the obvious differences in lifestyle, food choices and all the other factors affecting calorie intake and expenditure will dwarf any variation in an individual’s physical composition.

In order to gain weight, the maintenance calories can be increased by around 500 calories a day. Any more and the chance of the weight gain being muscle begins to slim down (unlike the person following this eating regime!). If you are especially small but dieting down to super lean levels, then you will almost certainly have to add in inordinate amounts of cardio to create the deficit. Unpleasant, but better than feeling like you are starving to death.

To lose weight you can reduce the maintenance calories by 500-1,000 a day. If a person is carrying a lot of body fat then it is better to use their LBM (lean body mass) instead of total bodyweight to calculate their calorie and protein requirements. To figure out LBM, you can measure body fat in various ways or just use your best guess (with similar accuracy).

You may be able to restrict calories much more than this, particularly if you have a great amount to lose. Whilst you could expect faster weight loss, it will be tougher, your workouts will invariably suffer and you begin to run out of options as your weight loss slows down. 

Reducing calories too cautiously means the person is trapped in a perpetual diet which provides more chance for slip ups, longer to lose strength, slow progress and disappointing results. In my experience, tentative dieting doesn’t work as the margin for error is too small – a tiny dietary slip up will undo all your work, but it really depends how much weight needs to be lost.

Expect that for every 3,500 kcals over or under consumed, a 0.45kg change in body weight will result.

However, in reality changes in weight don’t come easy and are often less than predicted. Worse, body composition does not change the way the tracked calorie expenditure would suggest. 

If you add or subtract 500 calories a day to your current intake your will gain or lose weight but only up to a point. As your bodyweight changes so will your calorie requirements. What was once an excess or a deficit will sooner or later become the new maintenance level.

What about your metabolism?

Whenever we eat, energy is required to process food, digesting and absorbing it. This is called TEF (Thermic Effect of  Food) and accounts for 20-30% of the energy from protein, 5-10% from carbohydrates and 0-3% of fat.

Fat has far more calories per gram and a lower TEF, so only 15g of fat would equate to about the same net total calories as 40g of protein. Generally speaking, the more you eat the more calories you’ll burn due to TEF.

This is a hollow victory of course, because you would have consumed more calories in the first place to create this effect and no food produces a negative calorie effect from eating it. 

On a side note, alcohol has 7 calories per gram and its TEF is around 20%. This is further complicated by your body being unable to store the calories but yet they still have a way of influencing your bodyweight when your metabolism seems to put other processes on hold (plus most alcoholic drinks contain other calories besides the alcohol and not to mention the ensuing kebab).

Unsurprisingly, eating less will mean you use fewer calories. But, before we start questioning the rules of thermodynamics, you will never restrict your calories to the point where your metabolism will slow to the point where you will gain weight or become fatter. Ever.

What about exercise?

Exercise has many benefits, but burning calories is not very high on that list. The calories we think we’ve used from exercise are a very complicated affair and if you think a workout can excuse whatever meal it is you’re trying to forget, then you’re going to be disappointed.

Many of the calories burned during exercise would have been used anyway from just existing, so it is only the few extra that the activity required that should be counted.

Only the fittest people on the planet can train hard enough or long enough to make much impact in their daily energy expenditure.

Those that can invariably do not need to use exercise as a way to burn calories and most likely having to increase the amount they eat in order to fuel such monster workouts. 

This is complicated further by the fact that the body dynamically adapts to intense exercise. This metabolic adaption allows someone to train harder and longer whilst burning off fewer calories. This means as the person is getting fitter, they are also becoming more efficient and reduces the expected energy expenditure (and rate of weight loss). Additionally, if the person were to get lighter because of the exercise, then their calorie requirements would be further reduced. Even extreme activity levels only increase calorie expenditure by 7%. 

Summing up (lame pun intended)

The calories you burn during an activity, or the calories you eat (or don’t eat) are only a small part of the maths determining your future bodyweight. But don’t lose heart – while it is true that NEAT has by far the biggest impact on your calorie expenditure, small adjustments to your life has a significant impact over a long time. Hence the advice to take the stairs instead of the lift, park a bit further from work and so on. Little adjustments cause tiny changes, but it all adds up. Read the “being active blog“. If you will make and stick to enough of these, switching from a very sedentary life to a very active life is going to be like night and day. Throw in exercise, adjust the calories you eat to suit your goal and you will be well on your way to making ‘calories in vs calories out’ work for you. Admittedly it is not as simple or as easy to predict as we are led to believe, but it does work eventually.

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