Relying on body mass index (aka BMI), the numerical measure of your height and weight, as an indicator of health is highly unreliable, according to a new University of California study. In fact, more than 54 million heavy Americans are wrongly labeled as unhealthy, the researchers say; these so-called “healthy overweight” men and women may have to pay higher health insurance premiums as a result.
But, even if you’re a fit guy, there’s been long-winded debates over the efficacy of BMI measurements as indicators of health and fitness despite the fact that measuring changes in body composition is one of the most effective ways to evaluate your diet and workout regimen, and lowering your body-fat percentage is crucial for getting six-pack abs and a chiseled physique.
So, what are the most accurate ways to track changes in body composition then? Well, there are tons of different techniques, each with their own set of pros and cons. We outlined the most popular methods to hit the market in recent years—and the ones that have been around for decades—so you can decide what works best for you.
Note: For the best results check your body composition every six to eight weeks to measure improvements and see progress.
1. Underwater weighing
What it is and how it works: Since muscle is much denser than fat, body density can tell us a lot about body composition. With underwater weighing, the subject is submerged and his density is calculated to estimate body composition. The downside is that you have to get wet, and you need to be submerged underwater which may not be comfortable for some. However, underwater weighing is an extremely accurate measure of body composition if you don’t mind going under.
2. Bod Pod (whole-body plethysmography)
What it is and how it works: As another method of measuring density, the Bod Pod measures air displacement to estimate body composition. The testing procedure is very similar to underwater weighing—minus the water. The main downside: Bod Pods are often hard to come by, and they can be expensive to use. However, they can be an effective alternative to DEXA and are extremely accurate.
Where to get it done: Check your local sports medicine clinic to find one near you.
3. Skinfold measurements
What it is and how it works: Skinfold measurements are done using calipers on several sites across the body. They take into account the amount of subcutaneous (directly under the skin) fat an individual has and use it to predict total body-fat percentage. The most common variations are the 3- and 7-site skinfold tests. Sites are slightly different between men and women, but the protocol remains the same. Skinfold measurements remain as a popular and widely used method of measuring changes in body composition since calipers are easy to use and found at almost any gym. For the best accuracy, avoid working out beforehand and have the same technician perform the measurements each time since each technique may be slightly different.
Where to get it done: Colleges and universities, hospitals, commercial fitness clubs, and sport physiology labs.
4. Bioelectrical impedance scales
What it is and how it works: Bioelectrical impedance analysis scales are a popular method of measuring body composition because they're inexpensive and widely available. You’re probably thinking how the hell a scale can tell you your body composition. (We did, too.) The device sends a small amount of electrical current (don’t worry; you don’t feel it) through one foot, up your body, then to the other foot. It analyzes and measures the electrical signal after it’s run its course and estimates aspects of your body composition based upon how quickly the current is conducted. Lean tissue and fat mass conduct electrical signals very differently so the scale can use conductance to estimate body composition. However, the accuracy can widely vary. You want to use the scale at approximately the same time each day for the most accurate results since your activity and hydration level can throw off figures. And use BIA in conjunction with other methods of measuring body composition to ensure accuracy and track results.
Where to get it done: Facilities will have their own scales, but you can also purchase the Garmin Index Smart Scale for your home.
5. Skulpt Aim
What it is and how it works: The Skulpt Aim is a device that measures body-fat percentage and the quality of individual muscles by simply pressing the device against major muscle groups. (You can even pair it with its accompanying Skulpt app to track progress, identify problem areas and weaker areas, and adjust your workouts accordingly. Using multiple electrode configurations and multi-frequency electrical measurements, Sculpt Aim can separate the condition of the muscle from the amount of fat in the surrounding area in a matter of seconds. In all, it can measure 24 different muscles, providing the fat percentage and a rating of the muscle’s fitness for each. You can even view a "heat map" on the app to conveniently track your strongest muscles and those that need improvement. To measure your body's muscle quality score and fat percentage, you'll measure four areas: biceps, triceps, abs, and quads.
Where to get tested: Anywhere if you purchase Sculpt Aim.
6. DEXA (Dual-energy X-ray Absorptiometry) scan
What it is and how it works: In a DEXA scan, X-ray technology is used to estimate lean tissue, bone, mineral, and fat across regions of the body with amazing accuracy. Not only will a DEXA scan let you know your precise body composition, but it will also break it down by body segment so you can see where you’re holding the most muscle and fat. X-ray technology makes DEXA scans extremely accurate but also harder to find. They can also be quite pricey. Check with your local physician to find one near you.
Where to get it done: Hospitals and facilities across the U.S.