Hi all, can anyone tell how accurate is the calories we burn showing in Google Fit app? Thanks!

[Midiwill]

Can someone explain is the calories displayed in the Google Fit app is correct or is it giving something else.

[moreless Administrator 7 stone]

Is this the guesstimate of calories burnt, Midiwill? I'm sure it will only ever be a guesstimate and not something I set great store by. As far as I'm concerned, exercise should be for health, fitness and well-being, not weight loss

[Midiwill in reply to moreless]

Hi moreless , not sure if it's a guesstimate. It shows both number of steps along with the calories. After the evening jogging it showed 1069 calories. I have a doubt?

Yes, it is a for my fitness but according to my personal challenge I put it under my weight loss process 🙂

[TheAwfulToad Visitor]

I get this question a lot in my professional life. The short answer is: don't take it too seriously. The "why?" is quite complicated.

If you want to know exactly how many calories a body is burning, and how, you need a gas analyser that records exactly how much oxygen goes in and how much carbon dioxide comes out. From this, you can determine a parameter known as the respiratory quotient (CO2eliminated / O2consumed) which varies between 0.7 and 1.0, depending on whether the reactions going on inside your body are being fuelled primarily from fats or from carbohydrates. Because these reactions are all well-understood, you can estimate calories burned from the volume of oxygen consumed; the magic number is 4.8kCal per litre of oxygen, assuming a RQ of 0.8 (which is typical under most circumstances).

Your fitness app, though, doesn't know how much oxygen you're consuming, or how much CO2 you're exhaling. It just takes a guess, based on the average human. The problem here is that metabolic efficiency varies dramatically between individuals - that is, the rate at which you burn energy vs. the rate at which your body does work ("work" being some useful physical act, such as thinking, digesting your food, or jogging). Your app starts from an estimate of work and efficiency for the act involved, and works backwards. For example, while pedalling on a cycle at 100W, the average body is burning energy at about 7METs (~1kCal/kg/hr). So if you weigh 70kg, and you're Mr or Ms Average, you're burning 500kCal/hr. Except you're probably not, because of the aforesaid individual variation. Athletes have more efficient bodies, and burn less food calories for a given power output. Untrained people burn more. Same sort of thing applies to jogging, swimming, and even to sitting around doing nothing.

A more philosophical answer is that it doesn't matter much. If you're training in such a manner that your physical performance is getting better - you're running faster, or for longer - you've achieved something useful. You can use your calories value to tell you whether you are getting better, and by roughly how much, because although the numbers include a certain inaccuracy relating to the difference between you and the assumptions used to make the estimate, that inaccuracy is in some sense "constant", because you are still basically you. If you see that you averaged 300kCal on the treadmill last month but you're now averaging 350kCal, you've got considerably better at running, and that's all you need to know.

Important: the calorie number tells you nothing useful about your weight loss, for a whole bunch of different (equally complicated) reasons.

[Midiwill in reply to TheAwfulToad]

TheAwfulToad I see.. Ha haa no need a gas analyser 😉

I was just curious about the number it showed as I'm logging everything. And because that cals that the Fit app showed made my daily log crazy to show that I have earned negative calories today!! Crazy! (It deducted my today's food intake and showed a negative number)

Okay, so I should not take that number serious anymore. I will just do my exercises until I fail for the moment 😏

Thank you for you explanation..

[S11m in reply to Midiwill]

It is a bit like estimating how many litres of fuel a car would take to drive from London to Birmingham.

If you know the size of the car and load, and can guess the efficiency of the engine, and you know how aerodynamic the car is, what the traffic is like and, assuming no wind... you might be able to guess within 10%.

Some exercise equipment measures your power output, and tells you, quite accurately, how much energy you have produced - but a system would have to estimate your fitness (how efficiently you convert fat into output power) to estimate how much fat you have burnt.

Given enough information about you, and from sensors, an app can estimate your efficiency... My Apple Watch 4 knows "everything" about me, including my heart rate, weight, age etc... and it estimates how many calories I use. It tells me that yesterday I used 2,442kcal "resting energy" and 1,033kcal "Active energy" or 3,475 total kcal, but another Apple App, using the same data, tels me I used 3,358kcals... but I am 110kg, and I walked 8km in freezing to 4C! I think this is why I have to eat a bit more to keep up to my target weight for the week!

As TheAwfulToad says, Calories used is relevant to weight loss, but you do not know how many calories come from burning fat, and how much comes from carbohydrates from your digestive system.