I’ve been absolutely shocked over the years how many times before races and events that I’ve heard someone around me say to their friends, “I’m ready for this, but I’ve been working out so hard but I’m not losing weight! I don’t understand!”. Before I started studying exercise physiology, I’d be sitting there waiting for the events to start and be thinking “huh, that is weird”.
After doing a lot of studying, the answer wasn’t quite what I would have figured. The biggest thing we need to look at in this question is your Basal Metabolic Rate (BMR). Effectively, this number tells you how many calories you’re burning just by being alive.
This can be calculated by the following equations:
BMR = 655 + (9.6 × weight in kg) + (1.8 × height in cm) – (4.7 × age in years)
BMR = 66 + (13.7 × weight in kg) + (5 × height in cm) – (6.8 × age in years)
Using myself as an example, at 6’1″ and 195 lbs and 37 years old, and after converting to metric for the equations, I have to eat about 1950 calories a day just to remain at my weight. However, this is assuming I’m bedridden. Any more activity starts adding to this by 20% on the sedentary end, all the way up to 100% more on the seriously working out high end. (Reference)
But this is where things get weird. As it turns out, running only burns about twice as many calories as walking. And, what’s super weird is that running or walking faster doesn’t change the amount of calories you’re burning to cover that distance.
So, if we ignore your BMR during the duration of a run, then a fast 5 mile run burns the same energy as a jogging 5 mile run. (Reference, and another Reference) The way scientists figured this out is by tracking how much oxygen you consume while working out.
You burn about 5 Calories per liter of oxygen consumed, which is a good guess of your calories because any run over 2 miles or so is going to be mostly aerobic (oxygen based) and you can figure your liters of oxygen consumed for running by calculating:
VO2 = 0.2 ml per kg per min / m per min × velocity in m per min
Unfortunately, this equation is hard as hell to use and it’s also in metric, so after some conversion to a more friendly format in imperial units we have:
calories burned on a run = 0.731 × your weight in lbs × the distance in miles you ran
So say I run a 5k in 25 minutes. At my 195 lbs over 3.1 miles, I burn about 442 calories. This is energy I wouldn’t have burned standing still. Notice, the pace at which I run does not factor into the equation for how much extra energy I burned. Also, going at a fast walk would only burn 221 calories since walking burns half the energy.
How does all this relate to losing weight, running, and exercising? Well, that’s a decent 5k time for most people and that’s the same caloric content as 3 cans of soda, 3 cans of beer, or 2 donuts. That’s nothing.
But, that’s the real answer here. If you’re wondering why you aren’t losing weight form running and exercising, it’s because of your diet. I’ve seen a lot of people say things like “oh, I worked out today, I can indulge a little”, but they over indulge in the end. Keep in mind even a marathon is only going to burn about 2000-3000 calories. My Buffalo Wild Wings Small Boneless Wings last night was almost 1500 calories by itself.
Eating properly is a whole conversation by itself, but for starters, try cutting out sugar and alcohol from your diet. These foods are empty calories anyways. To lose one pound of fat you need to burn 3500-400 calories more than you are consuming. Keep your protein high and you’ll retain your muscle too.
That’s all for now! Eat slightly less and you will start losing weight!