It's a common question: Why do some people have an easier time losing weight or building muscle than you do?
Sure, unhealthy habits are likely partly to blame, but what about your genes?
Dr. Dan Reardon is CEO of Fitness Genes. It's a DNA testing company that aims to answer that question. He says, "There's a lot of really great research that exists."
For about $200, consumers can buy a testing kit.
We enlisted a few Action News viewers from Unite Fitness to try it. They spit into a test tube, mixed it with a preservative and then mailed it to the Fitness Genes laboratory.
Dr. Reardon says scientists extract cheek cells to isolate DNA. They then test 43 different gene variations.
Some look at how your muscles react to different exercises. Others how caffeine affects you, and how fast you burn fats and carbohydrates.
Dr. Reardon says, "So whether the goal is getting fit, losing weight, specifically accelerated fat loss, building muscle or sports performance, we can really guide people into those goals using their DNA as a backbone."
Many of our testers were interested in finding out which workouts will give them the best results. Others wanted to know if they're genetically drawn to certain foods.
After several weeks, three out of our four testers received very detailed results.
Dustin Kidd, 41, of South Philadelphia tells us he struggled with his weight in the past.
He says his results confirmed things he already suspected.
He has a tendency to gain weight, but responds well to exercise.
But some results are confusing and seem to cancel each other out, such as his response to saturated fat. One copy of the gene showed greater sensitivity, the other showed lower.
DeAnna Diaz tells us she always seems to have 5-10 pounds she can't lose. Her results do show it might be tougher for her to lose those few extra pounds, but like many people, it says high-intensity, interval training should help.
Our third tester, Abby Watson also says her results fit what she expected.
She had lost 130 pounds in the past and says, "When they showed me the nutrition breakdown that would be ideal for my genotype, that was almost exactly how I was eating in terms of macronutrients when I lost weight."
It also said she metabolizes caffeine quickly. And because she had two copies of a gene looking at muscle strength, her results recommend more resistance training.
One gene indicated she tends to be able to control her appetite well. But she told us earlier, that's not the case when it comes to carbs.
Overall, she thought Fitness Genes was interesting. But also saw caveats on the report, such as that 'no gene acts alone. There are likely other significant genetic and environmental factors.'
Watson said, "I think when you're reading through this, it's pretty clear the science is still kind of young, and there's a lot they don't understand how all of these things interact."
And that's why there are many skeptics. Dr. Charlie Seltzer, a weight loss expert in Philadelphia, says genetic testing holds a lot of promise in the future, but we're not there yet.
"Looking at 43 genes in the context of our entire genome is not going to give us nearly enough practical information to be able to apply to a real-world situation to help someone lose weight faster," he said, adding at this point, a simple blood test may provide more practical information.
"So for example, if you're worried you may be predisposed to diabetes, looking at one gene is not going to be nearly as helpful as looking at your blood sugar on a blood test, which is covered by insurance."
Dr. Reardon agrees the science is in the early stages, but argues, "We are at a point in the process where we have enough of an understanding to start to apply these principles to peoples' lifestyles."
He says the test is best for people who don't know where to start, or for people who are looking to fine-tune their fitness.
One positive thing Dr. Seltzer says is if you buy the test, you may be more motivated to do what it says, eat healthy and exercise.
Fitness Genes is offering Action News viewers a discount on a DNA test. For information, CLICK HERE.
Can DNA test help you get in better shape?