In my last (stunningly well-read) blog, I started a series on how to get good information about nutrition, exercise and weight loss. Chapter 1 dealt mostly with how to decide for yourself if a "scientific" claim is probably valid and useful, so that you can make good choices for yourself, when there is soooo much conflicting information out there. ( couchto5k.healthunlocked.co... )

This is Chapter 2A: Weight Loss (Fat Loss)

Before I talk at all about how to lose weight, I want to clarify. What I really mean is, how to lose FAT. When dieting, it is also possible (even probable) to lose lean body mass, including muscle. This is not really the goal. Aside from helping you do things like walk, brush your teeth and type on the computer, muscle is important for a) running and b) losing more fat. I will not get further into that for this chapter - that is another chapter on its own. Suffice it to say - you may not be in your ideal body yet. To get closer, you should aim to lose fat and keep your muscle. (Yes, even if you are a woman who is naturally muscular. Trust me.)

Scales do not measure fat vs. lean. In fact, the easiest way to lose weight is to take your scale up a mountain, and weigh yourself there (less gravity). Or in a swimming pool (buoyancy). Weight is just the amount of pressure you put on the scale's pressure plate. So using the scale as your primary means of measuring progress towards health is tracking the wrong thing.

What is the right thing to measure? A very good question, with a few answers.

1) Body fat percentage is the actual measure of how fat you are. You need a certain amount of fat to stay alive, so it isn't the enemy. You just want to aim for a healthy body composition. Here is a chart based on age and gender: bodyspex.com/community.aspx... Depending on your age, women should aim for 20-30% and men should aim for about 10-20%.

How to measure this right thing:

The most accurate tools are a DEXA scan or a water-immersion test. These are very accurate, but very expensive and difficult to do. Bio-electrical impedance is another method; a very low electrical charge is sent through the body and timed. Fat is less conductive than lean mass, so the faster it goes, the leaner you are. The accuracy of these tests varies a great deal by the instrument, but it is fairly cheap, fast and painless, and can be self-administered. Skin-fold calipers are low-tech, low-cost and accurate when used correctly, but require another person to measure you, and that person needs to be able to do it precisely and with the right technique. A tape measure is extremely cheap and simple to use. It is best when done by another person, even so. And the results can be considerably more variable if you are not consistent with the snugness of the tape measure, or if you use a body fat calculator with your measurements that does not fit your body type. The least accurate, but still useful measure: your jeans and a mirror. If your clothes are getting looser, and you see more muscles, you are losing fat and probably not too much lean mass.

This is why people, even doctors, like scales. They are easy. They are concrete. A number flashes up at you and bada-bing you have your measurement. Is it less than before? Good!

But there is a way: You can still use any method with a fair degree of usefulness if you *track it over time*. You can measure yourself with a tape measure every week and write it down, and even if your calculator is inaccurate, and you yourself make mistakes with the measurements, you will still see a trend over time. Your estimated Body Fat percentage could be off by 10% (a huge margin) and still be useful if it is always 10% high, because you can see if it is going up or down.

Personally, I use a bioelectrical impedance scale. It was expensive, for a bathroom scale, but not terrible (about $60). I can then track my weight in total, my lean mass and my body fat, all by myself. I also use a tape measure to track if I am shrinking, and where. If I put my tape measurements into various online body fat calculators, the answer doesn't match my scale's measurement of body fat, but the trend over time for both is that I am losing mostly fat, and limited lean body mass. I would also be a strong proponent of the skin-fold caliper method over time, if you have a friend to help you. They are inexpensive. ($15 for the calipers. Friends, of course, are priceless.)

2) What about BMI? Isn't that the right thing to measure too? Sort of. Body Mass Index (BMI) is a mathematical formula that only has two variables: height and weight. It is therefore a glorified height-weight chart, designed so the BMI number means the same thing at every height and gender. (Healthy is 18.5-25, Overweight is 25-30, Obese is 30+) It has the exact same limitations as your scale does - namely it doesn't specify how much of your body is fat or lean or anything else.

That said, BMI is such an easy metric, that a lot of "good science" (see my previous post) studies have been done using it. There have been strong correlations found between having a higher BMI and having all kinds of illnesses: high blood pressure, joint problems, heart problems, diabetes, mortality, you name it. Not to mention having your jeans fit too tightly.

What does this mean exactly? Let's look at one example: using a whole bunch of test subjects, researchers found men with diabetes had obesity as an underlying problem in 64% of cases. Directly this means that a lot of men with diabetes had a BMI of over 30. Since those tests were not comparing body fat percentage with diabetes, we can even consider that some of those "obese" diabetic men probably did not have as much body fat as others. So we can conclude that regardless of body fat percentage, there is a greater likelihood to be obese if you are a man with Type II Diabetes. Although this particular reference does not state it, it is also accurate to conclude - from similar research - that being obese (having a BMI over 30) makes getting diabetes more likely. (en.wikipedia.org/wiki/Obesi...

You still with me? To put it simply, all these tests studying BMI rather than body fat percentage, still show increased risk of disease at higher weights (regardless of how fat or lean you are). So if your BMI is higher (or lower) than it should be, even if you are in good shape, it is worth confirming with your doctor that you personally are not at increased risk. Note: I have heard some criticism that research using BMI as a metric over-emphasizes the risk to individuals who have a healthy body composition, but are still heavy (big bones, lots of muscle). That may well be true, but like we discussed before, it isn't "good science" if it isn't properly studied and documented, and I haven't seen the evidence yet. (Have you? Do you have a link? I am interested if you come across something like that.)

***Note on BMI and children: The challenges with BMI (being a height/weight chart and not a body fat measurement) are even greater for children. Girls and boys differ, and everyone grows at different rates and times in their lives. To attempt to account for this, BMI charts for children are based upon percentiles, the 5th to 85th percentile being "healthy" and greater than that being probably overweight or obese. One of the biggest problems is when people use this reading as the actual determination of whether a child is too heavy. It is meant to be an indicator that more testing is needed to determine body fat percentage. Poor understanding of the tool, and stigmatizing a child who is healthy but muscular can lead to understandable criticism. It is important to remember that especially for children, BMI is just a first screen, not the final diagnosis. ( cdc.gov/healthyweight/asses... )

3) What about types of fat or how it sits on my body? I keep hearing about "belly fat" being bad. What is that all about?

There are actually a few types of fat in our bodies. They include intramuscular fat (marbled in your muscles), subcutaneous fat (right under the skin), and visceral fat (tucked in around your viscera - internal organs in the abdomen, aka belly fat). Fat in our bodies generates hormones which affect (among other things) our appetite, metabolism and insulin sensitivity. Subcutaneous fat and intramuscular fat create these hormones, but are not found to be as dangerous as excess visceral fat, where the hormones go directly into the internal organs and can wreak havoc.

So how do you know what kind of fat you have? It's pretty easy, actually. Fat on your arms, hips, thighs, bum, and so forth are subcutaneous fat, with possibly some intramuscular fat. Fat around the belly, especially if it is a pot-belly kind of situation, is the dangerous visceral fat. Taking measurements of your waist (at the narrowest point for women, the navel for men) and aiming to keep that smaller than half your height is a very good start. Example, a 5'0 person is 60 inches tall. Her waist should be under 30 inches. A 6'0 man is 72 inches tall, and should have a waist under 36 inches. This is the upper limit for a healthy belly size, definitely go for smaller if you can.

This is just as important as monitoring your total body fat and your BMI, because excess visceral fat (even if you are slim and toned everywhere else on your body) is strongly correlated with all those nasty diseases we talked about earlier: diabetes, heart problems, and so on.

4) What else do I measure? There are so many to choose from. Pay attention to anything that you personally suffer from, that your close family has, or that your doctor says is important. Is your cholesterol and blood pressure in a good place? Is your resting heart rate going down or staying low? All these things are good indications that you are getting healthier and taking good/better care of yourself.

***"Ok. Riiiiight. But How Do I Lose Weight, Errrr I Mean Fat?" I want to be size X and fit into the jeans in the back of my closet.

Here's how: do a bunch of the behaviors strongly correlated with Fat Loss. I will discuss them in the next post, very soon.