One of the things I like most about Trim, Healthy Mama is that they mention percentage of body fat in calculating your goal weight.
I'll admit it, I like numbers. I like having a logical way of deciding my goals, not just randomly pulling a number out of the air, or remembering what I weighed at a point in my life.
I want to know what I'm dealing with as far as pounds of fat versus the structure of the body. This takes your frame size into consideration without you having to 'guess' at whether you are large framed or small, or if you carry more muscle.
Body Mass Index, or BMI, is something totally different. It is nothing more than weight divided by height. It takes nothing more into consideration, and while good utilized as a tool in the over all picture, is sadly inefficient at telling you anything specific about your goals, in my opinion.
Determining your body fat, like all systems, can have flaws. Finding your exact body fat involved being weighed underwater on a special scale. Most of us can't easily do that, but there are home scales that use impedance to tell what your fat percentage is.
The issue with scales or handheld impedance monitors is that you must be well-hydrated for the most accurate results.
You can also calculate percentage of body fat using your measurements. You need a tape measure and a chart or online calculator to determine using this method.
Personally I like to use both the scale and calculator based on measurements. Neither is going to be perfect as they are both calculated numbers and not a direct measurement. It will give you a general idea of where you are at and you want to watch for body fat trending downward as you lose overall weight.
The THM authors recommend a body fat of around 25% for women. Healthy range for women is generally considered anywhere from 18-26% based on your age and fitness level. The normal, or ideal, range for men is 10-17%.
I'm personally shooting for 25%. I'm not young, and I know what my percentage of body fat was when i was 30 and working out 2 hrs a day. I think this is realistic and healthy for me.
When you get a percentage of body fat number then you have to determine the 'other side' of the equation. This would be your Lean Body Mass, or LBM. This includes all the bones, muscles and tissues. This is the number, that even with dieting, you don't want to see change.
If you consider your whole body to be 100% and your body fat + LBM = your overall weight.
example... a woman weighs 150 pounds with 30% body fat. Remember to change your percentage to a decimal!
you find the pounds of fat by multiplying: 150 x .3 which equals 45 pounds.
45 of your 150 pounds is fat.
This means that 105 pounds is your Lean Body Mass/LBM. You get this when you subtract the body fat from the overall weight.
You want to see this number (105) stay the same as your fat number goes down over time.
So you find your percentage of body fat and the pounds and your LBM percentage and pounds.
How does this help you find your goal?
If you are expecting your LBM to stay close to what it currently is, then you use it in the calculation.
You might gain or lose a few pounds in either direction so don't let that alarm you. Often people who are overweight or obese have higher LBM to support the weight that they are carrying, and they will see a decline a bit. Exercise can also help to increase or maintain LBM as well. You just don't want drastic drops.
To find your goal, you need to determine where you would like to see your body fat. If you are shooting for 25% body fat, then you are looking at a LBM being 75% of your weight.
You will use the 75% to determine your goal.
example: if my LBM is 105 pounds and I want to get to 25% body fat, then I want the 105 to be the other 75% of my weight. To find what my overall weight would be, I just need to flip my original equation:
105/.75 = 140
This makes my goal weight 140 pounds based on my current LBM.
You then can subtract this number from your current weight to see what you should need to lose to get to your goal.
example: current weight-goal weight gives you pounds you need to lose.
150-140= 10 pounds to get to goal
I think it is important to know how much fat you are carrying and not just randomly pick numbers, that may or may not be realistic, for weight goals.
There are several online calculators, but I like this one. Just disregard the protein and calorie recommendations here.