BOULDER (AP) – Gary Berg owns Boulder CrossFit and is the head trainer there. He has been a lifelong athlete and played basketball in college, before he coached it. He’s a certified personal trainer and fit, at less than 12 percent body fat.

And, according to the Body Mass Index calculator, he’s overweight and two pounds away from obese.

Berg is far from obese.

He shuns the BMI index, as many people in the health and fitness field do.

“The BMI scale is the worst possible thing you can offer somebody. It leaves out a huge factor: lean body mass,” Berg says. “The basic algorithm is flawed. A BMI system never comes into our gym.”

Scales aren’t always an accurate way to gauge health and fitness, either, he says.

Instead, he promotes a body composition test, which calculates lean mass, or muscle, and the percentage of fat. This can give people a more accurate understanding of their metabolic rate and how many calories they need to eat, which can help people lose fat (if needed) without destroying muscle, or help athletes grow stronger.

Plus, he says, a body composition test can help promote healthy fitness; if you lose weight through an unhealthy diet, your weight might go down, but the test also will show you have lost muscle and potentially even bone density.

“If you lose weight by starving yourself, you lose lean muscle mass first, and it’s a deadly spiral,” Berg says. “A lean, muscular body will have a higher metabolism and be able to process food better.”

That’s why Berg, as well as other gyms and CrossFit clubs across Boulder County, use body comp tests when they run fitness challenges, instead of doing it by the scale, “Biggest Loser” style.

Body composition tests have come a long way since the old-school caliper pinch test.

Today, you can find a variety of more accurate ways to get your body’s numbers.

The DEXA scanner, typically used to precisely measure bone density, can also plot muscle and fat prominence. But this machine is typically found only in medical settings, and it can run hundreds of dollars for a single test.

You might see the Bod Pod machine in gyms. This egg-like machine uses pressure to measure body composition, but its accuracy can be skewed by body hair or even lotion, according to Matt Preston, of Boulder, a microbiological nutritionist and certified fitness nutrition specialist.

The Anschutz center also does Bod Pod tests.

Preston prefers the InBody 230, a machine that uses bioelectrical impedance analysis to provide the muscle-fat breakdown with a 98 percent correlation to the much more pricy DEXA scan. The InBody scan costs $20 and takes about one minute.

Preston offers the InBody 230 at his business, Colorado Nutrition.

The machine provides quick, accurate measurements of fat, lean muscle, bone density and even water. It measures each limb, too, so athletes can identify muscular imbalances that could affect performance or lead to potential injury.

But the most important number the machine provides is the basal metabolic rate, Preston says, or how many calories your body expends by doing nothing for 24 hours.

Ninety-nine percent of his clients are under-eating – especially athletes, but also obese people, Preston says.

“It sounds bizarre, because we’re do trained to eat less, work out more, therefore you should weigh less, but it doesn’t work that way,” he says. “Yes, you have to expend more calories than you take in – that’s the law of conservation of mass – but we can’t be in this 2,000-calorie gap, because your metabolism slows down to match how many calories you’re taking in.”

Determining the right kinds of food and nutritional proportions is where his business steps in.

Colorado Nutrition, which opened a year ago in Boulder, sponsors professional athletes (cyclists, triathletes, runners) and teams and works with various local gyms. He says the InBody is used by NFL teams and the Mayo Clinic, but it’s not common around town because of its steep price tag.

Radiance Health in Louisville also offers the machine.

Then there is the water submersion, or hydrostatic, body composition test.

Boulder is the home base for Colorado’s only mobile hydrostatic body fat company, Body Fat Test Colorado.

That’s what Berg, with Boulder CrossFit, uses for his clients.

The premise: Your body weight is different on land than in water, and the difference, when applied to a certain calculation, gives an accurate measurement of the percentage of fat to lean muscle.

Roseanne Allen, of Louisville, launched the mobile tank in 2012. She is capable of traveling across the state, although she says she’s busy enough just along the Front Range, especially in Boulder County.

Allen, who has a degree in exercise physiology from the University of Northern Colorado, says she grew curious about her own body composition about seven years ago, after she started doing CrossFit.

“I started feeling better, my dress size dropped and I got leaner, but I did not lose weight,” she says.

The changes were substantial, but the scale didn’t reflect a thing. She says she wanted to know what was going on in her body.

She had learned about hydrostatic testing in school, and she says she considered it the “gold standard” body comp test. But she says she couldn’t find anywhere to get it done.

“I figured, if I wanted this, everyone else must, too,” Allen says. “As it turns out, it’s true.”