Sunday, March 11, 2012

Calories In, Calories Out

Calories In, Calories Out is Correct

The first law of thermodynamics (FLTD) states that energy is neither created nor destroyed and is conserved in a closed system.  Therefore if we take in more energy (calories) than we get rid of we will store/incorporate the remainder (often as body fat).  In other words:

Food (calories in) – BMR x Activity (calories out) = Change in stored energy

The actual equation is a lot more complex (see [1]).  The FLTD can be used to suggest that the reason people become overweight is from a calorie surplus by eating too much and exercising too little, and that the key to weight loss is to produce a calorie deficit by eating less and exercising more, because we can control food intake and activity level.  And this suggestion is completely correct [2]

Calorie Restriction Alone isn’t a Very Effective Weight Loss Strategy

We live in the real world, not metabolic wards.  People can go on diets and exercise to lose weight, but in response to dieting and weight loss there is:

  • An increase in appetite
  • A decrease in satiety from gut signals
  • A reduction in basal metabolic rate
  • Less of a drive to be physically active
  • A loss of lean body mass [3]

Willpower is required for calorie restriction, but willpower has its limits and most diets fail [4].  There's a reason why expressions like ‘yo-yo dieting’ exist.

More evidence against simple calorie restriction comes from an interesting experiment.  Rats were put on a regular diet or a fattening diet.  The rats on the fattening diet ate more calories and gained weight.  A third group of rats were placed on the fattening diet but they could only eat as many calories as the control group.  This third group gained 60% more weight than the rats on the regular diet [5].  Other examples include: low protein diets (<15%) can increase total calorie intake [6] and artificial trans fats can increase weight gain in an isocaloric diet [7]

An alternative strategy is to adopt a diet/lifestyle plan where you spontaneously adopt a negative energy balance with as few of the adverse side effects as possible.  For example: people on low carb, low fat and Mediterranean diets spontaneously reduced their calories and lost more weight than simple calorie restriction diets [8]

This isn’t a problem with CICO or the FLTD, but rather with the delivery of the information and the implementation

Beyond CICO

Body fat, appetite and satiety are all regulated by a number of hormones (see the table in [9]).  The role of these hormones is to ensure you eat the right amount of calories, not too much, not too little, and maintain a healthy weight.  Calories aren’t ‘bad’ or ‘unhealthy’.  High calorie foods/meals are supposed to make you full, not fat.  What is bad is when calories produce less satiety than they should or feeling hungry despite having 385,000 excess stored calories (50kg to lose).

Very few people want to be overweight, so what isn’t considered when someone says 'just eat less and exercise more' is why people who are overweight eat too much and/or exercise too little?  To borrow an analogy from Gary Taubes:

“Say instead of talking about why fat tissue accumulates too much energy, we want to know why a particular restaurant gets so crowded…If you asked me this question — why did this restaurant get crowded? — and I said, well, the restaurant got crowded (it got overstuffed with energy) because more people entered the restaurant than left it, you’d probably think I was being a wise guy or an idiot”…Of course, more people entered than left, you’d say. That’s obvious. But why?”

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