Just how much water should I be drinking? “About one-half your body weight in ounces every day, especially if you’re exercising,” Dr. Smith says. So the eight-cups-a-day rule applies only to sedentary women who weigh 128 pounds (sure as hell not me!). “If you consume an aggressive amount of fiber, another eight to 16 ounces a day is a good idea,” Dr. Smith adds. H2OMG! That amount of liquid — for me, 12 cups a day, minimum — requires serious effort. I fill up with about a liter at each meal, and I’m a peeing machine.

YOU SKIMP ON PROTEIN

Several studies show that high-protein diets result in more pounds shed, at least initially. Protein enhances the feeling of satiety and prevents your losing muscle as you lose fat. You also have dietary thermogenesis, which is the energy you burn to process and use the food you eat, on your side. “Your body expends more energy to metabolize protein than carbs or fat,” says Cari Coulter, RD, the program director for Wellspring Weight Loss Camp in Kenosha, Wisconsin. “So higher-protein diets make you burn slightly more calories.”

So how much protein do I need a day? “It depends on your weight, but most women should get 40 to 80 grams,” Dr. Smith says. To accomplish that, I have Greek yogurt (18 grams) or a couple of eggs (13 grams) for breakfast, and I eat a few ounces of lean poultry (25 grams) or fish (22 grams) or a heaping helping of black beans (15 grams) or lentils (18 grams) at lunch and dinner. I snack on a handful of raw almonds (6 grams). As a result, I feel fuller — sometimes so full I don’t even sneak a bite of my son’s ice cream (the way I used to whether I was hungry or not) — so it’s easier to keep daily calories in check.

MORE REASONS WHY YOU’RE NOT LOSING WEIGHT

YOU SIT AT A DESK ALL DAY

I log a solid hour of exercise almost every day, but outside of that, my time is mostly spent sitting in front of a computer. Much to my dismay, research finds that dedicated workouts simply can’t compensate for being sedentary the rest of the time. According to one University of Missouri-Columbia study, sitting for just a few hours causes your body to stop making a fat-inhibiting enzyme called lipase. Getting up and walking for just two minutes during each of those hours burns an additional 59 calories a day, according to recent research from the University of Wisconsin-Milwaukee.

Experts recommend setting a timer on the computer to remind you to move every hour, but what’s helped me is the Fitbit One . I keep this activity tracker clipped to my bra 24-7, and I won’t go to bed until I’ve logged 10,000 steps a day. To accomplish that, I heed some of those recommendations we’ve all heard a million times (“Take the stairs instead of the elevator,” “Park far away from the mall”). I even jog in place while brushing my teeth and watching TV. At first my husband and son laughed their skinny little butts off at me, but now seeing me hopping around the living room strikes them as normal. Walks are part of my family’s evening routine, and “How many steps do you have now?” has become the new “Are we there yet?” I’ve even given Fitbits to friends and family as gifts so we can see who takes the most steps. Move-more mission: accomplished.

YOUR NUMBERS ARE OFF

I’ve always considered myself a math whiz, so I assumed that I had the whole calories-in, calories-out formula down pat. Here’s how I determined how many I should eat a day: I got my basal metabolic rate (BMR, or the amount of calories I need to maintain my weight) using the online calculator at fitnessmagazine.com/weight-loss/bmr, and I entered “moderate” for my activity level, because I exercise regularly. That gave me about 2,400 calories a day. Then I added whatever calories I burn during my workouts (usually about 500), according to my heart-rate monitor. That meant I could eat almost 3,000 calories a day without gaining a pound (or nearly 2,500 a day to lose a pound a week). Sure, it seemed high, but I had used a calculator. It had to be right!

Not so fast, Coulter says. “The BMR calculator already factors in the calories you burn with your workouts, so you shouldn’t add them in again,” she explains. Math club membership revoked! All this time I had thought my daily needs were 500 calories higher than they really were. No wonder I’d been maintaining instead of losing.