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Is the yearly summer slim down slowing your metabolism?

Practical, professional advice from Ann Arbor exercise physiologist Mike Stack

Photo/Applied Fitness Solutions
Photo/Applied Fitness Solutions

Summer’s nearly in full swing and chances are many of you are several weeks (if not months) into your annual ritual of intense diet and hard exercise to get “in shape for summer.” Makes sense, right? I mean, we live in Michigan where it’s freezing for over the half year. Our bodies are covered up by snowmobile suits, full length parkas, and on those particularly hellish days, long underwear. Because of this, does it really matter if we’re covered up with a little extra fat as well? I mean, no one can see it, right? Well, that may be true, but what if I told you that the "seasonal" nature of losing and gaining weight is ruining your metabolism and will make it progressively harder to lose weight in the future?

I hope I have your attention now. Push pause on the diet for a few minutes and read on to learn more about the damaging effect of frequent and rapid attempts to lose weight.

Our Body Likes to Stay the Same

We’ve survived on this planet for thousands of years because our body is good at adapting and evolving in the face of stress. One of the most significant stressors the body is faced with is a lack of food. When this happens your body literally starts to eat itself (put a little nicer: you start to burn fat). Now I know you might be thinking, well that’s good, because I have a lot fat to eat, but it’s not quite that simple.

Your body (on an evolutionary level) doesn’t necessarily know the difference between 2018 A.D. and 2018 B.C. It doesn’t know you’re intentionally trying to restrict your calorie intake. It thinks there’s a famine. The crops have died, the animals have run away, and if the body doesn’t do something you’re not going to be around very long.

What does your body do? It goes into defense mode. It increases hunger hormones, decreases fullness hormones, and it makes food more highly palatable on a brain biochemical level (you actually release more dopamine in response to food when you’re restricting your calories). Last, but certainly not least, is the body’s most potent defense mechanism: the lowering of your metabolism. All of this is an effort to conserve your fat stores for the impending famine. We call this lowering of metabolism in response to a reduction in calorie intake adaptive thermogenesis and it is a very real phenomenon. 

I can hear you yelling at your computer screen right now: There is NO famine, crops are still here, so are the animals, I’m not wasting away – there’s no need to do this!!! Unfortunately, it’s not that easy; we just can’t tell our body it’s ok. This is one of our most critical self-preservation mechanisms at work, and every time you kick into high gear to that beach bod, it gets better and better for next time.

Adaptive Thermogenesis in Action

You’ve actually seen adaptive thermogenesis in action before, you just didn’t know what to call it. You might have called it by another, more common, name – a plateau. Have you ever reached a plateau in your weight loss and couldn’t figure out why? You’re still eating healthy, exercising (sometimes more and more) and you’re still not losing weight. What you thought was a plateau is really adaptive thermogenesis. 

The next logical question: why does this occur? The answer (at least right now) is we really don’t know. Most of the clinical measures we have to determine metabolism (thyroid testing, metabolic carts, etc.) don’t seem to be able to explain its occurrence. There are some complex scientific theories that are beginning to give us a better understanding of metabolic adaption, but we’re still not close to understanding the true underlying mechanism for this. 

A few things are, however, clear. First, it occurs: we see it happen all the time. Second, it can stop all weight loss even with high volumes of exercise and low calorie intakes. Three, the more often it occurs, the better the body gets at it (I know that sounds bad). Four (now for the good news), knowing it exists allows us to design weight loss programs to effectively account for adaptive thermogenesis, increasing our likelihood of long-term success. 

Let’s talk about three and four below.

Your Body is Smarter than You Are 

It’s actually probably a good thing our bodies are smarter than us. We do all kinds of crazy stuff that would make survival pretty hard without evolution and adaptation. Simply put, the human body has the capability to respond to stressors more efficiently over time. The more accustomed the body is to a stressor, the faster the response. Put a highly trained sprinter into the sprinting blocks, his heart rate will start to rise and he’ll start to sweat (in preparation for the sprint) before he even starts to run. Put me in the sprinting blocks and nothing like that will happen.

This efficiency evolution is great for the sprinter, but problematic when it comes to your metabolism. Each time you calorie restrict and lose weight your metabolism gets more sensitized to what’s happening. It’s almost as if the body is saying, “Fool me once, shame on you; fool me twice, shame on me.” That means the next time you attempt to restrict calories, all those defense mechanism will be heightened. Your hunger levels will rise more rapidly, you’ll find food even more palatable, AND your metabolism will drop faster. The net effect is each subsequent weight loss attempt becomes less and less effective. 

Work With, Not Against, Your Metabolism 

I know this sounds bleak, but the good news is you can develop a strategy to lose weight and keep it off. Follow these four tips to lose weight, keep it off, and maintain a healthy metabolism in the process:

  • Lose weight slowly. I know you hate me for saying this, but if you lose it slowly you won’t drive the body into such a defensive state and adaptive thermogenesis won’t be as much of a factor. Research suggests losing between 0.5-1.5lbs/week seems to be a realistic to maintain. This can happen by eliminating 2-3 unhealthy food items from your diet consistently.
  • Reduce items in your diet that aren’t proteins, fruits, or vegetables. Anything else is fair game, but keep these in your diet as they provide you with important nutrients that keep your body (and your metabolism) functioning well during weight loss.
  • Add in exercise. Increasing calorie expenditure through exercise helps keep metabolism going. You won’t have to restrict your calorie intake as much, which will result in a smaller reduction in metabolism.
  • Don’t Regain the Weight. As I said above, each time you lose weight your body gets more used to what’s happening to it. If you follow tips 1-3 you’ll be on your way to maintaining your weight loss. Please also remember whatever you did to lose weight, you’ll have to continue doing to keep it off, so make sure you’ve chosen exercise and nutrition that is sustainable.
  • Take Home Message

    The body is smart and has several defense mechanisms for combating weight loss. Each time you lose and regain weight you make it harder to lose it again. If you’re progressive and patient, applying the approach recommended above, you’ll lose weight, keep it off, and not have to worry about adaptive thermogenesis that much at all.

    Michael E. Stack is an Exercise Physiologist and CEO of Applied Fitness Solutions. AFS provides personalized nutrition and exercise coaching to clients in Ann Arbor, Plymouth, and Rochester Hills. 

    Learn more about AFS

    Next Week 

    If you've fallen victim to the "seasonal weight swing" look out for my article next week with tips and behaviors to get your metabolism back on your side!

    This content was produced in collaboration with our sponsor, Applied Fitness Solutions, without involvement from the All About Ann Arbor editorial staff.