Just when you thought it was safe to retrieve the forks and knives you hid during the “Are white potatoes a nutritious natural food or glycemic index hell tuber?” debate, scientists have given us another research study that brings up more questions than it answers. This time it’s about whether cardio or weight lifting produces better health outcomes in obese teenage girls and the answer is, well, a little surprising given the current zeitgeist in the fitness community panning steady state cardio.
The study, published in the November 2013 Journal of American Physiology, took 44 adolescent, obese girls and randomly assigned them to three groups: the aerobic exercise group did one hour of running on a treadmill or using an elliptical three times a week, the resistance exercise group did one hour of weight lifting three times a week and the last group did no exercise.
After three months of this, the girls were not only weighed but unlike many other studies on this topic also had their overall fat, visceral fat, liver fat and insulin sensitivity measured. (Kudos to the scientists for using a more rigorous measure of health than most!) The results were, well, see for yourself:
1. No one lost any weight. The researchers were curious to see if exercise without changing diet would lead to weight loss and unsurprisingly it did not. It’s one of the lesser known truths about fitness: exercise makes you hungry and your body will try to replace the calories you burned. In many research studies exercise has been shown to be an effective tool for keeping weight off but not for losing it.
2. The aerobic exercise group lost a significant amount of visceral fat, reduced liver fat and increased their insulin sensitivity. This was seen as a major benefit to their health as fat around your organs, fatty liver disease and insulin resistance are all red flags for many diseases including diabetes and heart disease. So even though the girls didn’t lose any weight they did definitely improve their health. Which leads to another lesser known (okay it’s widely known but just not talked about enough) truth about fitness: Exercise without weight loss is not pointless! It’s great for your health no matter what you weigh and regardless of whether you lose weight or not.
3. The resistance exercise group did not. Those poor girls had no significant difference in any of the health markers as compared to the non-exercising group.
4. The scientists noted that observationally the girls in the cardio group seemed to be having way more fun.
Reader Rachel, who tipped me off to the study, summed up her and my confusion thusly:
“This study really surprised me. It’s a little opposed to the “lift heavy for body composition” argument I see a lot (and have been believing!) Do you think other studies have focused on men, and that having an all-female test group makes the difference? Problems in the study itself? I feel confused! And I think you’re more likely to read the academic article linked inside the link than I am!”
Rachel is right. There has been a huge movement in fitness, especially over the last 5 years or so, to get off the treadmill and elliptical and trade your running shoes in for some heavy weight lifting sessions in the gym. Epitomizing this mindset is fitness writer (and one of my fave people ever) Jen Sinkler who made t-shirts that said, “I lift weights. How do I get my cardio? I lift weights faster.” The shirts sold out in hours. As CrossFit’s star rose, more girls headed to the gym in “beast mode” to smack tires, farmer carry weights and squat twice their body weight. It was a far cry from the days not too long ago when all women did was cardio and any girl caught on the weight floor was warned she would “bulk out” and look like a dude.
Rachel bought into that. I bought into it. Lots of you bought into it. So is it wrong?
Here are my thoughts on why you might want to take this new research with a grain of salt (because salt is also one of those things that used to be demonized and is now coming back into favor! See what I did there??)
1. Kids mess everything up. I’m kidding. No I’m not. You should see my house. It looks like what would happen if the Lego guys took Barbie’s dream house hostage and it all exploded in a cloud of glitter-covered Bakugans. Anyhow, my point is that just like you really can’t take adult study results and scale them down for kids, you also can’t necessarily extrapolate from kids to adults. Children are not miniature adults.
2. It’s not a dichotomy. You can do both weights and cardio and you probably should. So what if you have limited exercise time and you want to know which to focus on? Circuits! It’s very simple to pull together a short but intense routine involving both weights and bursts of anaerobic cardio. All of the most effective programs in my personal experience involve both.
3. They were doing the cardio and the weight lifting wrong. First, lots of research has shown that shorter, intense bursts of cardio are more effective for fat loss than slogging on an elliptical for an hour but the study wasn’t comparing HIIT against steady state. Second, if you’re lifting weights for an hour you’re probably doing something wrong. I’ve seen a lot of people “lift weights” by taking 5 minute rests between sets and only working the muscle groups they can see. The girls weren’t “lifting heavy” or doing a functional routine. If you like working out for an hour than go for it (heaven knows I enjoy an hour long sweatfest sometimes) but you don’t have to go that long to see positive metabolic changes. It would have been more interesting to me if the researchers weren’t essentially comparing out-dated cardio to out-dated weight lifting.
4. I think it’s super telling that the researchers said the aerobics girls had more fun during the experiment. Traditional cardio is actually a really great way to bond with friends. One of the things I like (possibly the only thing I like) about being on a treadmill, step mill, elliptical and the like is that usually your heart rate is up enough to make you sweat but not so much you can’t do other stuff like watch TV, flip through a magazine or… talk to your buddies! You can chat while weight lifting too but you generally don’t have that side-by-side aspect of both of you standing on immovable pieces of equipment. So I would guess that the girls in the cardio group might have been putting more energy into it while the girls doing weights may have been going through the motions but not enjoying it. Just a guess.
One thing that Rachel brought up that I do think is super important though is that this is an all FEMALE study. There are not many of those in the fitness world and for a long time the theory was that a body is a body is a body so women should just be treated like men with lower centers of gravity. Of course that isn’t true. We girls have some unique physiological, metabolic and, yes, emotional differences that make fitness different for us. So perhaps the old canard about women needing more endurance while men need more strength has some truth to it? Only more research will tell.
The researchers of the original study concluded, “Given the superior improvements in metabolic health with aerobic exercise and the enjoyment factor, we propose that aerobic exercise may be a better mode of exercise for adolescent girls of this age group.”
But what are my conclusions? In the end, I’m not sure how I feel about this. For as long as I’ve been exercising I’ve found cardio stuff more fun. I love Zumba, Turbokick, step class and anything else dance-y. Weight lifting holds no joy for me. I used to have fun doing it with the Gym Buddies but that was mostly because they were a riot rather than the routine being fun. Because of that, I used to lift heavier and more often back in Minnesota. I’ve really really dropped the ball with the weight lifting over the past 6 months. I do it but I do it in the fastest way possible and mostly body weight stuff or kettlebell circuits. And – research: party of one! – I feel like I’m “flabbier” and have less muscle and tone. So I guess my personal conclusion from all of this is that girls need both to be healthy. You have to balance doing what you love with being a balanced person.
What do you guys think about this study? What have you noticed in your own life in regards to weights vs. cardio? Which is your favorite?