I have been hearing for some time now that when it comes to weight loss, exercise is not king. Diet is paramount. I mean, the NY Times said it, so it must be true.1 To be fair, they cited many reputable studies in their report that seem to indicate exercise only goes so far in weight management. The amount you can burn in a single exercise session is easily erased by something as innocent as a second helping of dinner or a favorite sweet treat. Also for many, hunger increases after exercise and leads to overconsumption, alter erasing or even worsening the calorie deficit they were striving for. I get it. I can see how exercise may not be the key piece in the giant puzzle of weight loss.
That being said, I have always had a nagging suspicion that exercise is more important than we think. We already know it helps for a host of issues other than weight loss, including mood / depression, cardiovascular health / blood pressure, blood glucose regulation, hormone balance, improved immune function, etc. People who exercise, on the whole, are healthier. Period. But I still had this feeling that given the right duration and intensity level, exercise has a key role in weight management.
Then this study popped up online2, giving us new insight into what might be going on with our metabolism when we exercise.
Researchers from Karolinska Institute in Sweden found mechanisms in mice by which exercise counteracted fat storage and reduced inflammation. A compound called kynurenic acid, induced via exercise, was the key.
To understand the big picture, backtrack with me real quick. Preceding this study, in 2014, this same group originally published that kynurenic acid in the brain, produced via exercise, supported improved brain function. Exercise produces a sound mind, they declared.
Building on that, they conducted this recent study where they introduced kynurenic acid orally in mice with the goal to reach all the tissues, not just the brain. These mice, while eating a high fat diet that promoted obesity and elevated blood glucose, stopped gaining weight and in turn converted more of their white fat to brown fat, which is the type that is more metabolically active. They also had improved blood glucose control despite no change in diet.
The theory is that the kynurenic acid in the fat cells promoted this conversion from white to brown fat, while kynurenic acid in the immune cells enhanced anti-inflammatory properties.
These two factors, the increase in metabolically active fat and decreased inflammation, both assist the body's ability to burn fat as energy and prevent excessive fat storage.
Sounds promising! Lace up those shoes! But then this begs the question, what type of exercise should we be doing to get this benefit?!? What is the magic formula? Running? Light walking? Pilates? HIIT cardio? Cross Fit? Yoga?
Unfortunately, this study does not lay that out as the kynurenic acid was administered orally rather than induced directly via exercise. A little digging however, and another paper provided exactly that information: endurance exercise.3
Ah, I knew it! I had a suspicion that the time and intensity of exercise mattered. Quick and dirty workouts have their place, but nothing takes the place of a good ol 'get-your-heart-rate-up-for-a sustained-period-of-time-type workout.
What this study showed was that subjects undergoing sustained cardio, in these cases an hour or longer, produced high levels of kynurenic acid in their muscle tissue within an hour after exercise. Subjects doing exercise that involved shorter bursts of intense energy did not see these benefits.
So there you go. Cardio for the win, right? Well yes, mostly I suppose. I think the key takeaway is to remember cardio is important and has an important role in weight management, but don't let that cause you to overlook the roles of muscle conditioning, toning and even plyometric-type activities to overall strength and health. Varying up your routine to prevent injury and strengthen your body overall is so important as well!
If you are now thinking about what kind of exercise is safe for you, let me put out a quick disclaimer here. I am no exercise physiologist. I work with food to help people lose weight, however exercise is such a key piece of that puzzle. Also I have been an avid exerciser since my early 20's so I tend to talk about it frequently with my clients. That being said, if you need specific advice as to what is safe and appropriate for you to be doing, please consult with your doctor, a physical therapist, or even a certified trainer to develop a plan. My role is to educate that exercise is important. For tailored guidance, particularly if you have injuries or other limitation, see a professional! *
If you feel OK starting up something on your own, let me put out a quick plug for one of my favorite online workout websites, Fitness Blender.com. For approachable, achievable and FUN workouts, this site is the best. Run by a local Seattle couple, they have FREE online workouts for any fitness level and any length of time you happen to have available. I'll be honest. We don't always have time for sustained cardio, do we? These workouts can easily fit in your day, whether you have 15 minutes to spare or an hour.
The truth is, though, if you are really serious about shedding that weight for good, regular exercise needs to be a part of your routine.
So yes, do lace up those shoes and get moving because the evidence is clear: exercise, and specifically cardio, supports fat reduction. Of course you have to watch your diet, too.
* Always check with your doctor before starting any new type of exercise program. Should you choose to try something new, always start slow and always be aware of proper form. If in doubt, consult a trainer or teacher to master the fundamentals before increasing intensity. Basically, start low and slow to avoid injury!