For the second part in this series of the science behind weight loss I will explore how to achieve a calorie deficit through decreased intake and increased physical activity.

As I discussed last week, in order to loose one pound per week, it is necessary to average a 500 calorie energy deficit per day.  The easiest way do do this is by some combination of reduced calorie intake, and increased physical activity.  Having said that calorie counting is not particularly easy or straightforward, and definitely requires time, dedication and planning.

There is a saying in the business world that you can’t manage what you don’t measure.  This applies well to eating and exercise.  Most of the time when we eat, the last thing we are thinking about is recording the number of calories consumed, however this is exactly what is necessary in order to accurately track calorie intake.  Nutrition information can be found on the sides of food packets, but be careful to read exactly how large the serving size is.  In restaurant chains nutrition information should also be available on request.  It gets more difficult when estimating the calorie content of home cooked food, and often it is necessary to go back to the nutrition labels of each of the ingredients.  There are also online calculators – www.livestrong.com – and iPhone apps – LoseIt! – that can help.  These resources also provide methods of tracking calories consumed over time.  Of course paper food logs are another option, and the ‘points’ program from Weight Watchers is a simplified way of doing this too.

I would strongly encourage anyone interested in loosing weight to track their calorie intake for at least a few weeks.  It will make you much more aware of how many calories certain foods contain.  As one example, a small seafood chowder at Legacy hospital with a bread roll contains 520 calories, but 102 of these calories are from the butter on the bread roll.  Would you still have whipped cream on your mocha if you knew it increased the calorie content from 220 to 330?

Exercise is another important part of achieving that energy deficit.  Exercise make you feel better, gives you energy, reduces your risk of serious health problems, and expends energy.  Again it is important to measure and track how many calories you are burning, and again the internet is a great resource.  Some examples:

• One hour of low impact aerobics burns 381 calories
• One hour of slow bicycling burns 476 calories
• One hour of gardening burns 286 calories
• One hour of moderate pace walking burns 219 calories
• 10000 fast steps measured using a pedometer represents 500 calories

Looking at this it is evident why it is so difficult to loose weight through exercise alone.  It would take over an hour a day of at least moderate impact exercise to achieve that 500 calorie deficit.  Having said that the more calories burned through exercise, the healthier you will feel, and the less restrictive your diet will need to be.

In summary, reduced calorie intake and increased exercise can help to achieve that 500 calorie per day energy deficit.  It is important to track energy balance as you can’t manage what you don’t measure, free online tools can be a great help with this.  In the next post I will cover the importance of resting metabolic rate, and later how bariatric surgery can help.