When you get home from a ride, the number of Kcal burned and Kiljoules of work burned on the Garmin device might say 1761 but how does this number guide our nutrition? Should we be eating 1700Calories? The number assumes 100% mechanical efficiency. We are closer to 20.3% efficient, therefore we should take this data point of kilojoules of work completed and multiply by 0.203 to arrive at 351.9kCal, this is much more reasonable. Also having your resting metabolic rate measured by a sports physiology testing center at a university or private clinic, we do this test in our Bridgetown PT studio, this helps to know what your resting metabolism needs to maintain your weight so if you add the calories burned from the workout you can create a slight Calorie deficit by eating slightly less than this number most days of the week. Calories in calories out is not everything when it comes to healthy weight balance and health but it is one important part. get these numbers wrong and it wont matter which healthy foods you are eating, if you are over fueling you will be missing the progress of your fitness from the watts/ kilogram. Also to know how to fuel effectively for big training or racing days having these numbers will ensure you do not underfuel and have a lack of ability to complete the workout or get dropped, this is a sure way for your training not to progress and lead to chronic fatigue and a number of health and performance deficits due to underfueling.