Hey Gang!
I recently wrote a post on an innovative method to improve consumers’ abilities to make sensible food purchase choices https://www.46sportfitnessrehab.com/new-food-package-labelling-coming/. “Activity based” food labelling is supposed to allow the consumer to get a quick idea of the amount of calories contained in a food/drink item. By displaying the duration of a certain activity (i.e. running, cycling) it would take to burn off said calories, you get a better idea of activity to caloric equivalents. In theory this should give consumers yet another tool to drive sound and sensible food and drink purchasing options.
While this in theory appears to be an excellent means for consumers to base food purchasing decisions, it could also prove to be somewhat misleading. You need to have a basic understanding of what constitutes ‘caloric expenditure’ in the context of the different modes of activity, how hard you are working (intensity), and duration. Your own physical make-up is another factor which one must consider. For the purposes of this post we will focus on some of the more common activities such as locomotion (walking, jogging, and running), cycling, and swimming.
Let’s start with an individual’s physical make-up. This can be a complex discussion in itself due to the great variability in people’s genetics, age, sex, consequences of previous lifestyle choices (more on this in a subsequent post), socio-economic status, and more. 
Most devices (tech wearables, HR monitors, accelerometers, GPS devices, etc.) rely upon formulas or algorithms which take certain variables such as your age, weight, height and based upon measuring your performance factors, such as distance, # of steps, velocity, intensity, power, and duration, they will give you a somewhat accurate reading (hopefully) of your energy expenditure (kcals burned) during a certain activity.
Generally speaking the heavier you are, with everything else being equal, the more you will burn for a given activity. Let’s take jogging as an example. For argument’s sake we have two 44- year old woman of similar stature. They are neighbours and have been jogging together for years. Their fitness levels are fairly equal and their best 5 km run times are nearly identical. Sarah is a former varsity soccer player and is very muscular. Diane is a former ballerina so while muscular in her own right she is far less bulky than Sarah and she has a smaller bone structure. Sarah weighs 25 lbs more than Diane due to the differences in body composition. Despite the fact that their runs are a similar distance at similar intensities, Sarah burns more calories than Diane for the same duration and distance of activity.
Now while mode of exercise also plays an important role in determining caloric expenditure there is evidence suggesting that there is less variability than once thought. Let’s take cycling versus running. Since individuals normally differ significantly in a number of pertinent factors (age, height, weight, fitness level, experience, etc.) related to the calculation of caloric or energy expenditure let’s consider the case of Dan, an age-group recreational duathlete.
Dan trains pretty hard for an old fart. He does his long run and long cycle respectively on Saturday and Sunday each weekend. Due to the demands of his race, the cycle workout is typically much longer than his run workout. Since both workouts are meant to put in volume (distance) and intensity in each workout is fairly constant, we can estimate that Dan’s caloric expenditure for the same period of time during each activity will be somewhat similar. Or can we make this assumption? In reality there are many factors not even yet mentioned which need to be considered. Course selection (hilly vs flat), wind resistance, running vs biking economy (how efficient is Dan at running vs biking), and so on.
Some will argue that when cycling you are supported by the bike and you are really only using your lower body. Many will contend that it is much tougher to get your HR up in cycling so other factors being equal you will burn fewer calories per unit time. While there is some merit in this argument there is conflicting evidence. Swimming vs cycling and running also demonstrates similar issues.
There was a time when it was suggested that swimming did not do as much for caloric expenditure as running or cycling. Since swimming is an unnatural movement for most people and there is resistance with regard to water, it would be normal for one to assume that swimming would expend more calories per unit time especially since it uses all parts of the body. This would be especially true if you sucked at swimming. But on the other hand does the buoyancy of swimming decrease energy expenditure? This may depend on how technically efficient you are in the water.
You also need to consider the thermogenic effect of cold or warm water. Swimming or exercising in cold water seems to actually increase the rate and absolute amount of calories burned as compared to swimming in warm water which reduces the rate and absolute amount of calories burned.
The bad news is cold water is not exactly pleasurable and if you swim consistently week to week, your body will adapt and compensate so you won’t continue to burn more calories. Some studies have indicated that swimming also causes an increase in appetite post-swim which encourages over eating and of course, added caloric energy intake.
Needless to say whatever modality you use in your health & fitness program is probably what you are comfortable with and sustainable for the future. I could care less if you use a pogo stick to keep up your activity levels. If it works for you then BRAVO!
I realize that all this stuff seem to be confusing and quite contradictory. Hell, I sure know that I am confused half the time. What the hell, eh? The point I am trying to make is to take generalizations with regard to energy or kcal expenditure with a grain of salt. There are sooooo many factors and variables which can influence energy expenditure that to accept either this or that as the gospel truth is inherently flawed.
While the activity based food labels are a step in the right direction the actual values stated are not necessarily correct. They are generalizations and should be viewed this way. Keep things in perspective and seek out a qualified fitness or health professional to help you wade through the mountain of data found on that information highway we so affectionately refer to as the internet!
If you would like to discuss this further or have any questions please feel free to contact me!