Weight loss calculator.

[JimC]

I am making a weight loss calculator and I would like you guys to test it. Tell me if it seems accurate, have any suggestions or if you find any bugs.
It's based off of the Harris Benedict formula.

Cal-Calc | Calorie based, weight loss calculator

Also, the weight loss per year is kind of inaccurate since it is non-linear. As you lose weight, the amount of weight you are able to lose is reduced.

[Angela]

Hi, JimC. I can't be bothered to break down my day by the hours spent in various levels of intensity. Maybe if you simplified that part so that all I had to enter was: how many hours of intense exercise do you do each day? and then let the program figure out the rest. It's too much trouble to count it up -- "well, is working at the computer resting? how about cooking? etc." The payoff is not high enough for me to figure it out.

That's just me; others might be willing to work out their hours, especially those who have defined specific goals and want to look awesome in their James Bond swimsuit before the end of Summer.

[JimC]

Ah yeah, I see what you mean. The reason I have that in there is because the level of exercise greatly influences your calorie burn. Yard work, for example, is only half as effective as running.

Each level of exercise has a multiplier, and if someone walked around for 4 hours, but then someone else went running for 4 hours, it would be absurd to tell them that they lost the same amount of weight.

Perhaps I could give better descriptions for the levels of intensity.

[Shamou]

Jim! Somehow I find the "Your daily activities (in hours)" a little confusing... I spend about 4 hours on the PC... now, what it that...??? I'm not resting and and not doing mild exercise... so what is it...???

I believe that there should be a slot for strictly mental activities because nowadays most people spend most of their time (working hours) doing it...

However, the rest seems to be working just fine...

.

[JimC]

I tinkered with the descriptions. Computers would fall under resting, unless you do intense mental activities like programming and gaming, I guess you could put those in light work.

[Brutha]

Also, the weight loss per year is kind of inaccurate since it is non-linear. As you lose weight, the amount of weight you are able to lose is reduced.

And you lack the necessary math skills?

[JimC]

Originally Posted by Brutha

And you lack the necessary math skills?

thanks? I could easily make it accurate by re-checking each week or month with the new weight, but I am too lazy. It's simple arithmetic, my math is fine.

[silicon toad2000]

nice constructive criticism from the moderator there.

I tried it out, It doesn't seem quite right.
For me the maximum caloric intake for weight loss was very much too high. I know from experience if I consume that, my weight will balloon out very quickly.

[NotesMaeve]

My minimum caloric intake was high for saying most of my activity is sleeping, sitting, etc. (I'm 5' 8" and 116.) 1300 calories? No way. I would be huge.

[JimC]

It may seem high, but I got the numbers more or less correct from the equation.

The minimum calories is your BMR... Your body spends that much just doing it's job, it doesn't include activities.

if (gender=="male") {
bmr = eval(66 + (13.7 * weightkg) + (5 * heightcm) - (6.8 * age));
} else if (gender=="female") {
bmr = eval(655 + (9.6 * weightkg) + (1.8 * heightcm) - (4.7 * age));
}

Source: BMR Formula

[Keith]

JimC,
Mine is way too high. Yeh, I'm big but it says I'll be losing weight at 4000 calories per day!

The minimum looks right for the BMR but you seem to have an error in the multiplier for the maximum. If I put myself in as resting 24 hours a day (just to make the math easier - I do a little more exercise than that) your calculator says:

Minimum: 2355
Maximum: 4090

The Harris-Benedict multiplier for being sedentary is x1.2, for a total of 2826 which sounds plausible. Of course, if I wanted to lose weight I'd have to drop below that or do more exercise. 4090 calories per day is about right for "very active (hard exercise/sports 6-7 days a week)" which is a multiplier of x1.725.

NotesMaeve,
if you're getting less than 1200 calories per day, that's too low. Your body will go into starvation mode which is not healthy. If you would balloon at 1300 calories, something is wrong.

[JimC]

Alright, apparently sleep isn't a factor in your "resting" state of activity. So when you sleep, the only exercise you get is your metabolism.

So I have added a section for sleeping. This lowers your maximum calories, but it may still seem a little high. Surely, this has to be correct now.

Thanks again everyone.

[Keith]

It still looks high compared to Benedict Harris. What formula are you using to work out the multiple?

[JimC]

The old version (before I added sleep as a factor) already included BMR in the multipliers. In other words, instead of saying:
min = bmr
max = bmr + exercise
it should of been:
min = bmr
max = exercise

So that would explain the big max amounts.

Also, because it's in hours, that means you must do x continuous hours of that activity without taking a break. If you're lazy like me, that's really hard, so I have added the ability to use decimals. (Be sure to put a 0 before the decimal [0.5])

Thanks everyone (besides Brutha) for the continuous testing. Hopefully I have it down now, if not, let me know. =)

If I can get this down accurately, I will add some kind of food planner or calorie chart and some other features if anyone suggests.

[Keith]

I suspect it's probably wrong to set BMR as the minimum. According to this site describes BMR as the number of calories you'd burn if you stayed in bed all day. Wikipedia says much the same thing in a more verbose way.

Take for example the scenario where I do 8 hours of light exercise and spend the rest of the day resting. That requires 5288 calories. My BMR is 2362. That's almost 3,000 calories below maintenance! That seems potentially unsafe.

A rule of thumb for healthy weight loss is to reduce your calories 15-20% below maintenance but never below 1800 for men or 1200 for women, and to a total drop of no more than 1,000 calories.
In this case, my range for the day in question would be 4288 to 5288.

[m0vingon]

My calculations were off as well. I know that when I calculate manually, my max caloric intake should be about 2800, but on your calculator I got almost 3800.

For the low end, it said almost 1700, but that would be a 2000 calorie difference, which is too extreme for anyone. Something was definitely off for my calculation.

Sorry

[JimC]

I hope you're saying it's off based on your past experience with professional tests and not just "doesn't seem right".

It's not like I pulled these equations out of my ass. I am taking the average multipliers and using the equation from:
Calorie Burning Chart, Calories Burned Per Minute of Exercise By Weight, Calorie Burning Chart, Exercise, What About Exercise?

and the BMR equation:
Weight Loss - BMR - How Many Calories Should I Eat - How to Calculate Caloric Needs - Basal Metabolic Rate Forumla
Which is the same equation for the site you gave me.


To say that I should just multiply it by a percentage is rather innaccurate. There are a lot of other factors like height, weight, age, sex, body type etc...
So I think the activity multipliers are better. It works fine for me and I also did it on some family members.

Sure you are being honest with the activity? Remember that it's continuous time and discludes breaks.

Originally Posted by Keith

Take for example the scenario where I do 8 hours of light exercise and spend the rest of the day resting. That requires 5288 calories. My BMR is 2362. That's almost 3,000 calories below maintenance! That seems potentially unsafe.

I highly doubt you do 8 hours of continuous light exercise. The initial calculation for this is by minute so it does not include taking breaks. If you really do nonstop excersize for collectively 8 hours in a day, 5288 seems perfectly reasonable, remember that the max includes your BMR. If you spent that 8 hours sitting, it would just show your BMR as your max. The minimum is not the amount you should consume, it is the minimum amount to be safe, do not consume less than that.

8 hours being 480 minutes, go to the site mentioned above and plug in 480 minutes and you should get similar results.

[Matthew Shea]

It seems unrealistic to make people figure out how many hours a day they spend doing each of the listed categories of activity. I imagine most people would end up making some pretty inaccurate guesses in that regard. To do this accurately would require keeping an activity journal, something most people would not do.

As far as I'm concerned, one of the most effective tools I've seen (and use daily) is The Google 15. It keeps a 15 day moving average of your weight so you can easily see your overall weight trend.

[JimC]

Well, the purpose of the calculator is for people who plan to lose weight. If anyone is serious about losing weight, they should certainly have their activities planned out.

I just posted it here for testing purposes.

That Google module is pretty sweet though.

[Keith]

Originally Posted by JimC

The minimum is not the amount you should consume, it is the minimum amount to be safe, do not consume less than that.

I doubt that BMR is a safe minimum when the maintenance requirement (ie. the maximum) is significantly higher. BMR is just enough calories to maintain a bedridden body that isn't even eating.

Do a couple of days serious exercise on that level of food intake and you will crash, driving your body into energy conservation mode. ie. You'll feel like crap and start retaining weight as your body goes into starvation mode.

Originally Posted by JimC

To say that I should just multiply it by a percentage is rather inaccurate. There are a lot of other factors like height, weight, age, sex, body type etc...

It's a percentage of the maximum, and the maximum already factors in height, weight, age and sex. (Body type is very hard to quantify. I note that your calculator doesn't include it, presumably for that reason).

I'm not questioning your math. I think you've calculated both the BMR and the maximum (maintenance calories) just fine.

What I'm questioning is your assumption that BMR is a safe minimum level of calories even when maintenance calories are much higher. Can you cite anywhere that indicates that this is the case?

Originally Posted by JimC

I highly doubt you do 8 hours of continuous light exercise. The initial calculation for this is by minute so it does not include taking breaks.

Call it 2 hours light exercise, 1 hour heavy exercise (which is a reasonable weight-loss routine) then. You get the same problem - attempting to function on thousands of calories less than maintenance.

[JimC]

Alright I think see what you're saying. So should I just make the minimum equal to about 15-20% less than the maximum? I kept thinking maintenance = bmr for some reason.

[edit]
Fixed: Minimum calories now equals Max - 20%.

[JohnJohnJohn]

Thanks for developing this! It is very cool and surprisingly, very rare on the net. I looked everywhere for a calculator that would also predict rate of weight loss given an amount planned to be consumed.

I am currently on a plan to lose 135 lbs by reducing my calories to 1500 per day. You calculator accurately predicts my first week's weight loss. But, as you admit, your results become increasingly inaccurate for a longer program like mine.

If I accept your prediction that I will lose 4.3 lbs per week, I'd think I would be at my target in just over 31 weeks. BUT, since the weekly weight loss decreases as I lose weight and keep the input (1500/day) constant, in reality it will take me more like 40 weeks to hit my goal. (And of course this all assumes I stay on plan!)

If you want to make your calculator truly useful you can easily calculate the estimated time to hit the target by simply calculating each day's predicted loss, subtracting that predicted weight loss and then using that as the basis for calculating the next day's loss and so on until the target is reached. I created a cool Excel spreadsheet that does just that.

Another suggestion I would make is don't make me enter 0s for unused fields. If my hourly entries total to 24 then assume I meant 0 for the remaining fields!

Finally, to make this tool the best it can be I'd recommend you allow me to choose how to enter my activities. Leave the current method in place for nuts like me who like calculating every little thing. But make it simpler for the "regular" folks who would prefer to just check a box. Maybe offer them something like this (from the Harris-Benedict equation?),

* sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2

* lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375

* moderatetely active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55

* very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725

* extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9


But kudos to you for the progress you've made on this!