How Accurate Are MFP Weight Loss Estimates? One Example

I'm a sedentary 55 year old male who started counting calories and trying to burn off 70+ pounds of fat about 3 years ago. Three months ago, I joined MFP after seeing that the online diaries are so easy to use. I'm nearing my goal weight (I'm now 5 pounds over my healthy weight at age 18) and I know the last few pounds are the hardest to lose. But I thought I'd calculate my predicted daily weights using my food and exercise diaries and the assumptions that MFP makes and compare them with my actual weight measurements for the past 90 days.

MFP assumes I'll burn 1900 calories per day on average unless I do cardio and that 3500 calories is one pound of body fat. If I calculate what tomorrow morning's weight will be by taking today's calorie intake minus today's burn (1900 + cardio calories) and then divide that difference by 3500 and add the result to today's calculated weight, then I get the following chart. The red line shows my calculated weights assuming my first day's weight of 165 pounds and all my diary information since then is correct. The green line shows my actual daily weights (I weigh every morning after I awake and pee) and the blue line is a five day running average of my actual weights (which I show to smooth out some of the daily ups and downs in my daily measurements). You'll see that except for the first few days, the predicted and actual figures differ by only about two pounds over the entire period and even match the little ups and downs, generally.



Frankly, I'm shocked at how good these calculated weight estimates are. I assumed that counting calories might be a good trend indicator at best since I assumed that there are so many ways for inaccuracies in the input data that the actual weight predictions would be way off. Just consider all the sources of error: what did I really eat today?, what was in it? (I eat out a lot and often have to guess), how much did I eat? (I usually can't weigh what I eat and rarely know how much oil was used to cook it, for example), are the MFP food database calories accurate?, does my body absorb all the food I eat?, how much do I really burn in a day if I don't exercise? (i.e., how good is that average value of 1900?), how much do I actually burn exercising? (i.e., are the database figures reliable for me?), does that 3500 calories per pound of fat apply to me?, are there extenuating circumstances for me?, and really just how honest am I with myself?

Here are a few personal statistics after 90 days: I target 1500 to 1800 calories per day intake every day but averaged 1908 (min = 1358, max = 3207). I target one hour of vigorous cardio (a 6 mile run or elliptical; seldom any strength training) 6 days per week plus a few miles of brisk (4 mph) walking on some days. I actually averaged 607 cardio calories per day which is supposedly equivalent to about one hour of elliptical seven days per week. My goal is to burn more calories than I consume 6 days out of 7 with the one day per week as an intentional rest day. I actually burned more than I ate on 74 of the 90 days which is about right. My calculated weight loss over 90 days based on all that data is 15.4 pounds and my actual weight loss was 17 pounds. My food diary is open and I'd be happy to answer any questions.

A few personal conclusions:

1. I don't know how well this works for anyone else but I find this (strongly) encouraging and even motivating. I would recommend simple calorie counting to most people who want to lose weight. I don't know if it will work for you. I only know it's been pretty accurate for me.

2. I'd recommend keeping track of at least the big calories. I'd focus on the oils and other fats (don't waste time looking for the calories in your gum or unsweetened ice tea) and try to get the big numbers as accurate as you can. For calorie burn, I'd focus on intentional, vigorous cardio exercises (don't kid yourself by trying to count calories burned walking to the mailbox or mowing the lawn; sedentary people do those things, too, and they're probably already included in your non-cardio calorie figure).

3. Focus on PROCESS (i.e., not progress)! Did you eat healthy foods in healthy amounts and do vigorous cardio exercise for a long time TODAY? If so, sleep well tonight! If not, I hope you still sleep well tonight but before you go to bed isn't there something you can do to change that?

4. Yes, progress is important, so monitor it. Don't fear daily weighings but don't get overly discouraged or overly cocky based on one noisy data point. Only use your daily weights to get a rough trend of your progress but only over longer periods like weeks. And consider what you might achieve if you could change your daily in versus out by just 100 calories. Over a long time, it will count. That's probably just a brisk walk around the block every day.

5. I have a job, a wife, and things to do and don't want to spend my life doing unimportant things. You likely have similar feelings. Don't make a life out of dealing with trivial stuff. Do the big things and move on.

6. Be honest with yourself and smile.

Good luck to you!