Why does every calorie tracking app give a different target calorie count for the same goals?

Question

I'm trying to improve my diet and exercise more. My personality is one that responds well to number-juggling systems, so I'm thought I should try those calorie-tracking apps you can get on smartphones.

I installed three of them (MyFitnessPal, MyPlate, MyNetDiary) to try them out and see which I liked best.

I entered the same info into all three (5'6" male, 31 years old, 256 lbs, desk job, targeting 1lbs lost per week). But they all recommend different daily calorie targets, with a difference of >600 calories/day between the highest (MyNetDiary) and the lowest (MyPlate).

Why are these recommendations so different? Is there really this much controversy over how many calories a person burns in a day? Which benchmark should I trust?

Answer 1

Because they're all based off vaguely defined math formulas which were created by various scientists that used questionable methodologies in an attempt to make a generic consensus on what people need to eat.

They are best guesses based on a user's age, weight, height, activity level, and sometimes bodyfat percentage. However, everyone's caloric need is different. Those apps want to work for as many people as possible, so they may do some further adjustments based on their own observations and data. MyFitnessPal, for example, has been accused in the past of artificially lowering calorie assessments because they know most people using their app are pretty bad at recording their food. So if they lower everyone's estimated calorie count by 10%, more people will lose weight, be happy, and stay with the app / recommend it to others.

If weight-loss is the goal, then ultimately you want to use more calories than you consume. You're aiming for a very standard and reasonable goal which is good. What you can do is to just choose the app that you find is the easiest to use, and use their calorie estimates for four weeks. The reason being that when you start a diet, you'll probably see a dramatic drop in weight the first couple weeks (it's mostly artificial), so you want to give it some time. If you lose weight at or close to your goal, then just keep on using it as-is. If it's really aggressive, then increase your calories slightly because it's underestimated. If it's more conservative, than decrease calories slightly. Adjust in the app if it allows; otherwise you may need to just make a mental note.

Answer 2

I'm a personal trainer who has had a lot of clients use these apps, though not as much these days, so I could be a little out of date.

By far, the issue I, or my clients, ran into is all hell would break loose the moment they would enter their activity level.

The first issue is people way, way overestimate how active they are. For most using these apps, they qualify as beginners fitness wise. One example of an error I would see is while the person may be active, because they're a beginner, practically all their exercise feels hard. In their mind then, they're working out hard, so they're very active, or burning a lot of calories, etc.

In reality though, you're not burning more calories just because you feel you're running, when in reality, you're jogging.

The next issue is the apps use all different kinds of methodology to arrive at a calories burned number. I've had plenty of clients tell me they burned 1,000 calories from their hiking.

Here's a paper for you,

–Constrained Total Energy Expenditure and Metabolic Adaptation to Physical Activity in Adult Humans

Here is the money image from the paper:

What that paper found is there is a plateauing of how many calories you'll burn in a day from activity. No, this does not violate physics. It's fairly simple. You, for example, run a lot in a day. The rest of the day you may be more likely to sit more than you otherwise would.

It's not just voluntary either. In a more extreme sense, if you're a female who runs a lot, your body may start shutting down reproductive abilities to conserve calories. (This is why so many intensely exercising females lose their period.)

More details on the study.

That study has been out for years now. I'm not sure I've even seen it discussed in the fitness community, much less even tried to be accounted for when calculating people's daily calorie needs, nor am I sure that's even doable when you see how much variability there is. (Look at how spread out those dots are above!)

This may be a little off base for your personal situation, if all you've put in is desk job for activity, but the larger point is still there: we've given people an enormously false precision as to how many calories we're able to know they burn per day, from a theoretical model. Even at low activity levels. Notice the very low activity levels in that image above. You can see a 5x difference in calories burned (which was tracked with radioactive isotopes aka a legit method).

The moment you ask the app to project weight-loss for you, you're asking it to project calories burned for you, which is a crapshoot.

The only way to do this is the practical model: eat a certain amount per day (the apps are quite good for this aspect), track your weight -you are your own benchmark- and go from there.

It's still a matter of calories in vs calories out, but the calories out is not straight forward. The body has all kinds of tricks. You might start eating less, but it might start burning less. Of course, at some point, you'll lose weight. Any client who told me eating less calories didn't work, I'd simply respond, "what if I locked you in a jail cell and never fed you?" That usually got the point across.

Answer 3

Whatever its internal initial formula (even if it cheats!), calorie/kilojoule tracking apps are programmed to alter slightly as they get more data about your habits and your body's response to those habits. The graph that they build of energy in / energy out, and some other key metrics, is all what makes the most difference. It is a matter of constant measuring and adjusting (which the app can help you do by showing you your history) rather than a matter of the magical golden formula of "only eat this" that is only in a specific app.

I say this based on the fact that I am in the same boat as the OP, and I have been trialling ways of using technology to lose weight. My past failures were in using one of the apps you mention, "MyFitnessPal", but I don't think it was specifically the app. As mentioned above, any generic formula used to determine fitness is generic and can't understand anything specific about your personal metabolism.

I am now using "Lose It!", and it functions very similarly to "MyFitnessPal", so this isn't really an app comparison. The things that I have found of extra benefit have been:

1. Pairing KJ intake with an exercise goal in KJs. Since I have apps to help me with this and I can pair them, I can track inbound and outbound KJs together rather than just focus on food.
2. Setting goals I can realistically hit without it being too much of a shock to the system. I don't want to feel hungry or tempted by things, so this time I have been trying to balance my macro-nutrients against each other rather than the simplistic mechanism of culling one thing entirely.
3. Having other people to do this with / compare notes with. Even though I am not really in for having gym buddies, it has been helpful to have help in talking over whether I should adjust my diet and exercise with people who have or are going through the process of doing it properly.

Overall, my advice is to echo DeeV and pick the app you find easiest to use. Keep using it to measure things regardless of which diet / exercise plan you use so that you can keep a track of your progress. But I will say that my job is also in data, so maybe this is purely my bias!

Answer 4

Why different? Formula's as mentioned: MFP uses a more recent Mifflin BMR formula that scales better for obese, other sites use Harris BMR based on 1919 study that has even been tweaked in later years. MFP uses an activity factor based on more recent WHO study, other sites use the same Harris 1919 study activity factors. MFP stops male minimum eating goal at 1500, not sure on other sites.

But even with those differences, it shouldn't lead to >600 difference between goals if all info is the same.

Pick whichever one allows you to deal with food easily so you actually use it.

Other method - log some common eating days as true as you can be - see how many calories you are used to eating at current activity level. If you were currently slowly gaining weight - call it eating 250 more than maintenance. Subtract 500 from maintenance for weight loss, and use that if activity is staying the same. Just find some calories to cut out of current eating style. If starting an exercise program, well, now burning more, eat less than that new amount.

Answer 5

Forget the apps. Last I checked, the research shows that these things don't help people lose weight. For example, see this: If you're rooting for smartphones to solve all our health problems, you're not going to like what the researchers found. Here's what does work: Time Restricted Eating (TRE). Check out Dr. Satchin Panda on podcasts. Or, if you can read science, check out some of the research. I've lost six pounds since I started TRE about two months ago. I have an eating window of between seven and eight hours. I have never, ever done any kind of dieting before this. However, the research on TRE is so solid, that I embarked on the first diet of my life. The thing about this diet is that you can literally eat anything you want, although if you eat good food then your obviously going to get more benefit. TRE is the thing that works. Forget everything else.