# Weight Management

## October 12th, 2020

-   So, let's talk about reaching and maintaining a healthy weight!
    -   A "healthy weight" is a weight you feel energetic and fit at, one that doesn't put as at increased risk of chronic health problems, and that you can realistically maintain through good eating and physical activity
        -   This doesn't have to be a single number, but a range that's healthy for your age, gender, etc.
    -   Now, less than 1/3rd of the population was overweight in the 1960s; now, it's 70% of people in the U.S.! No state has less than a 20% obesity rate!
    -   OVERWEIGHT means you have a BMI between 25.0 and 30.0 (or a weight 10%+ higher than your recommended ); obesity is a BMI of over 30.0 or higher (or 20%+ recommended weight)
        -   "Obesity is different and more serious than being overweight"
    -   BMI is your weight relative to your height; it doesn't directly measure your body fat (and so rarely used for diagnostics), but it's strongly correlated
        -   A BMI of ~18.5-25.0 is pretty normal for a healthy person
        -   A BMI of less than 18.5 is underweight
            -   This is ALSO dangerous, and can lead to malnourishment, nutrient deficiencies, low energy, heart complications, low body protein/fat, a worse immune system
        -   MORBID obesity is a BMI of 40 or higher, meaning your weight is DOUBLE healthy levels
        -   Again, BMI isn't perfect; it's inaccurate for people less than 5 feet tall or for highly muscled people whose weight doesn't come from fat
            -   This is why some highly athletic people can be considered "obese" by BMI alone even though they're actually quite healthy
            -   ...but for most people, BMI IS a decent estimate of their body fat levels

-   So, how do you measure body fat more directly?
    -   Some low tech ways are to just look in a mirror, look at your clothes size, look at your weight, etc.
    -   Higher-tech ways of accurately measuring body fat composition include skin calipers (margin of error), hydrostatic weighing (displaces water), "bod pods" (air displacement), BIAs (send a current through the body), etc.

-   Now, fat isn't all bad - we NEED some fat to survive (to regulate body temperature, store energy, cushion organs)
    -   Our body weight should be at LEAST 3-12% "essential fat" for men and
    -   STORAGE FAT is excess fats that we store energy in, but aren't necessary for living
        -   Overall, men should have 10-22% of their weight from fat, and women should have ~20-32% fat, for healthy living
    -   You can measure abdominal storage fat via waist circumference measurements; women should be <35 inches, men should be <40 inches
        -   However, WHERE your body fat is stored matters a lot. CENTRAL OBESITY, where a lot of fat is gathered around your stomach, is more dangerous than more evenly-distributed body fat
        -   There's also VISCERAL FAT where too much fat is stored in the fat around the internal organs, which are dangerous, can cause excessive fatty acid releases and metabolic syndrome, increasing bad cholesterol, etc.
            -   Because of this, you can have a decent BMI, healthy body weight, and even appear slim, but STILL be obese by your body fat percentage (and thus subject to increased disease risk)
        -   SUBCUTANEOUS FAR is the fat immediately under your skin; it's not great, but it's less harmful to your health than visceral fat

-   Let's also talk about ENERGY BALANCE, which is the ratio of energy you use to the energy you take in (via food)
    -   Ideally, you want this to be balanced, for the calories in to equal the calories used
        -   POSITIVE energy balance is when you're taking in too many calories, and you can become overweight; NEGATIVE energy balance is when you don't get enough calories and are underweight
    -   Your energy needs are determined by your age, weight, gender, basal metabolic rate (BMR), thermic effect of food (TEF), your physical activity, etc.
    -   BASAL METABOLIC RATE (BMR) is the amount of energy you need for basic physiologic functions (breathing, heart pumping, etc.)
        -   For a healthy adult, this is between 1200 and 1800 calories - ~50-70% of your calories
        -   More muscled people have a higher BMR, since muscles require more energy to maintain than fat
    -   THERMAL EFFECT OF FOOD is the energy needed to disgest, metabolize, and store food (~10% of your energy)
    -   RMR includes your daily activities, taking up the remaining 20-40% of of your calories
    -   1 pound of fat = ~3500 unburned calories that your body's stored

-   Now, OBESOGENIC environments are ones that promote too much food intake, unhealthy foods, and discourage physical activity (intentionally or unintentionally)
    -   Places where walking is difficult or dangerous, or with plenty of fast-food restaurants and not many good healthy places, might fall under this