Sitting on the runway at London Heathrow airport a large airliner carries 60,000kg of aviation fuel ready to power five hundred passengers and baggage across the Atlantic ocean. 7 hours later the same plane touches down in North America weighing almost 50,000kg less.
Like mechanical machines ripping through their fuel supplies, the human body loses weight when it expends more energy than it consumes. Whilst we don't have fuel-guzzling jet engines we do have trillions of hungry cells which burn energy in three broad categories.
Basal Metabolic Rate (BMR) accounts for the all energy required to sustain core body functions and makes up a significant proportion of daily expenditure. Total BMR value is largely dictated by age, body size and how much lean mass we have.
Thermic effect of feeding (TEF) accounts for the energy used to digest, absorb and assimilate the food we eat and makes up approximately 10% of daily expenditure.
Physical activity accounts for the energy spent moving. Unsurprisingly the more we move, the more we burn. For sedentary folks physical activity will account for a small percentage of daily expenditure whilst for an active individual the value can be much higher.
An example metabolism at work:
To ramp up the speed of a car's engine we hit the accelerator. In similar fashion the body has its own pedals which we can press to increase energy output and shed more weight.
- Strategy 1 - Boost BMR by increasing lean mass through resistance exercise
- Strategy 2 - Increase the TEF by switching to a whole-foods diet
- Strategy 3 - Increase your daily levels of low-intensity physical activity
Strategy 1 - Since basal metabolic rate is largely dictated by levels of lean mass adding some muscle to our physique through regular resistance exercise will increase the amount of energy burnt at rest. Not only is muscle a useful metabolism booster, it also helps hoover up blood glucose, adds tone and definition to our body, helps combat ageing and improves our physical capabilities
Strategy 2 - Processed food is more easily digested than its whole food counterpart. In practical terms this means you absorb a higher percentage of processed food calories. By eating more whole foods you increase the workload on your digestive system thereby reducing net calorie intake. Furthermore, this benefit doesn’t even take into account the increased nutritional density and appetite regulating qualities of whole foods.
Strategy 3 - NEAT (non-exercise activity thermogenesis) is a scientific term used to describe the amount of calories we burn via general movement spread throughout the day. Examples include walking, climbing the stairs, standing up, carrying bags, changing posture and playing. Dr James Levine has spent much of his professional life studying the effects of NEAT and concluded that it can account for huge differences in daily energy expenditure. In an age dominated by the chair ramping up levels of low intensity movement can have a profound impact on our waistlines. In the words of Dr Levine, we must get up and move.
Of course, no discussion of human energy balance would be complete without mentioning the other side of the equation… energy intake.
It took the passenger jet seven hours and thousands of miles to shed some 50,000kg of liquid fuel, yet the same tanks could be topped up in a matter of minutes upon arrival. The lopsided nature of this equation holds true for the human body too. No matter how well we rev our metabolisms it can be easily outgunned by consuming too many calories.
We must focus our attention on both the inputs and the outputs for optimal weight loss results.
- Get Up! Why Your Chair Is Killing You And What You Can Do About It by James Levine
- Barr SB and Wright JC. Postprandial energy expenditure in whole-food and processed-food meals: implications for daily energy expenditure. Food Nutr Res. 2010 Jul 2;54.