‘She’s got hollow legs’. ‘I only need to look at a biscuit to put on weight’. It is not news that some of us make more effective use of our calories than others. Are there ways to turn more of us into the ‘hollow legs’ type?
We need energy even if we appear to be doing nothing, because our bodies are always doing something. The energy needed to keep our life processes (heartbeat, breathing, digestion, temperature regulation, tissue repair) running is measured in calories. This is used to define our resting metabolic rate (RMR) which is measured in calories per hour per kilogram of weight.
For most people, RMR is an easy 1 calorie per kilogram per hour. Tot that up for someone weighing 70kg, and it makes for 1680 calories per 24 hour day.
If you are wondering how all this is measured, it involves being in a room that records oxygen used and carbon dioxide expelled. This equates to calories used. There are also a lot of samples to be taken!
The energy demands of our bodies vary not only with our weight, but with body composition, age and health. Those with more muscle will have a higher RMR. Don’t take this as encouragement to reduce body fat too far – too little body fat is as bad as too much.
As well as building muscle, exercise itself can change metabolic rate. The mechanism is not fully understood, but studies have shown that RMR increases during exercise, and more importantly and stays higher for up to 24 hours. This is the ‘afterburn’ effect. High intensity exercise can add up to 100 calories to the rate, while moderate exercise burns 60 calories extra per day.
It isn’t a huge amount but it makes a difference over time. Yet more reason to throw some exercise into your routine.
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Some people put way too much focus on the sentence "we need energy even if we appear to be doing nothing", as so many people grumble about being overweight when they don't move around much!! It continually baffles me. We are all in control of our weight and metabolism.
All the scientific details just confuse me. I just know that exercise helps me burn more calories and increases my metabolism, that's enough information for me.
I don''t think anything compensates for being tall and energetic. My partner seems to eat anything and never has weight issues, but he is 6ft and a busy person.