Tuesday, October 15, 2013

On Metabolism and Eating

This morning I broke down and turned on the heat. If not for the small people, I would have gutted it out for a few more days? Weeks, maybe? But it's cold in here and somehow I feel like a better mother for having turned it on.

Today I am going to talk to you about metabolism, which is often called the body's 'furnace.' So really, I was kind of excited to turn it on... thinking what a wonderful metaphor it was for my blog post and wow, I was going to have some great insights to share since I'd just turned on my own furnace.

Well, I don't. I don't understand how our furnace works. I just flip a switch. My Darling Husband understands how the furnace works. I suppose I could ask him, but he tends to go into such painstaking detail that my science-feeble mind can't take it all in. As I've said before, I'm not exactly Bill Nye, the Science Guy.

In the same way, I didn't really understand my own metabolism and how it works, so I engaged in some exhaustive research (this is hard-hitting journalism, people.) Here is a little primer on metabolism:

What is metabolism?
We only tend to think of metabolism as the rate at which your body burns calories. In reality, it is so much more. One article I read described it as "the sum total of all the chemical reactions in the body." Just so you know, I read very deep, scholarly articles, not just Self magazine. I read the kind of articles that refer to fat as 'adipose tissue.' And they don't tell you that 'adipose tissue' = fat. So, FYI.

Metabolism occurs in two distinct parts: catabolism, or 'destructive' metabolism, and anabolism, or 'constructive' metabolism. Catabolism is the process of breaking down what we eat and drink for energy. That description grossly oversimplifies the process, but still, that is more in keeping what I've always thought of metabolism doing. In fact, the metabolism is also responsible for building, storing and repairing cells in the body (that's anabolism), so our bodies are constantly cycling through these processes. (This paragraph proves I didn't just read Self magazine.)

In Bob the Builder terms, catabolism is like Muck the bulldozer and anabolism is like Bob and Wendy. I know, everything is suddenly clear to you now.

How is metabolism determined?
The bulk of the calories we use in a day just sustains the basic functions of living--breathing, pumping and circulating blood, brain function, etc. This called the basal metabolic rate (BMR)--that's the number of calories you would need if you were lying in bed all day doing pretty much nothing. I know, it sounds kind of nice, but I don't think it would be, because you wouldn't be able to snack much.

There are calculators on the internet that can help you calculate your BMR, but those are just estimates. Your BMR is highly individual. Part of it is genetically predetermined, but it's mostly related to your size and the amount of muscle you have. Muscular people have higher BMRs. Very large people have higher BMRs also, because it takes more energy to sustain a larger body.

This is one of the reasons strength training is so crucial for fat loss. As an overweight person loses fat weight, his BMR begins to drop because he just isn't as big anymore. If he builds some muscle, his BMR will increase again. Yay! We love muscle.

The rest of your caloric needs are determined by your activity level, and this is where NEAT (non-exercise activity thermogenesis) comes in. NEAT, as you will recall, is how much you  move around all day doing pretty much everything but exercising. Yes, your workouts burn calories, but your NEAT really helps in kicking your metabolism into gear. The cycles of catabolism and anabolism are initiated by the requirement of energy. Whenever you move around you're doing your metabolism a favor.

How does eating influence metabolism?
Your metabolism also gets a (little) boost from eating. This is called the thermic effect of food (TEF). Your body uses some of the calories you eat just to digest and break down the food. Don't get too excited, though--it's not much. Scientists estimate it's roughly 5 to 10% of the caloric total of your meal. So digesting a 400 calorie meal requires only 20 to 40 calories. Umm, that's not much. The TEF for eating protein is higher than the other macronutrients (fat and carbohydrates.) Research has indicated that eating a regular pattern of meals increases TEF, but really, the metabolic increase isn't huge. Sorry.

Of course, some people are going to do whatever they can to eek out whatever metabolic benefit they can, so they say, 'that's it! I'll eat more protein!' That's great. I love protein. By all means, eat protein at every meal. But still, if you eat more protein than your body can use, it will be stored as 'adipose tissue.' You can't get around it. You've got to burn what you eat.

Lately I've noticed a trend in weight loss articles. Invariably there is someone who says, "You may not be losing weight because you're not eating enough! You're going into starve mode and you need to eat!" Yes, this is possible. 'Starve mode' occurs when you cut your calories so drastically that your body anticipates a famine and slows everything down. You start burning calories at a slower rate and your body holds on to it's fat stores to keep you alive.

Honestly? I really don't think most people struggling to lose weight are in starve mode. Years of yo-yo dieting can screw up your metabolism, contributing to weight gain, but studies have shown that most people tend to overestimate the number of calories they consume by as much as 20%, and the bigger the meal, the greater the disparity between perceived and actual consumption. People write those articles because, let's face it, we all like the idea of eating more. If I think you are going to tell me something I like to hear, I'm more likely to buy your book or magazine. Sad, but true.

And this is the problem with bald science--scientists look at the numbers, the data, the research and say, 'do x' or 'don't do y.' But you have to factor data in with human nature. People like to eat. If you tell people, 'you have to eat or you'll go into stave mode!' some of us will run with it. The next time you're in AutoZone and feel a little peckish you think, 'I have to eat! Terrible things will happen if I don't eat!' So you grab a bag of Doritos (yucky) instead of waiting a half an hour to have a decent lunch. You're not going to go into starve mode in a half an hour. You're going to have a little adipose snack. I don't even know why an auto parts shop is selling Doritos, but that's another blog post entirely.

Anyway, you can maximize your metabolism through eating in the following ways:

1. Eat breakfast. Oh my, breakfast--so important. It gets everything going. If you're not hungry in the morning, eat less the night before.

2. Eat regular meals. It's better to consistently eat three meals a day than it is to eat two on Monday, six on Tuesday, four on Wednesday, etc. Your body adapts to a regular pattern.

3. Some people suggest eating frequently is better for metabolism, but I don't know, I found inconsistent research on this. This might be one of those really individual things.

Proponents of frequent eating say it helps to regulate blood sugar and keeps the metabolism humming along throughout the day. Some people swear by frequent eating, and by 'frequent' I mean eating every two to three hours, except when you're asleep. This translates into five to  seven feedings a day.

In practice, the problem with eating more often is that it can be difficult to limit your calories at each feeding. I think some people hear 'eat more often' and just add snacks without eating less at breakfast, lunch and dinner, thus increasing their total caloric intake for the day. If you need to lose fat, you must have a caloric deficit. You must consume less than you are burning through activity. There is really no way around this.

I don't want to sound down on snacks. I like snacks. I like food. We seem to have developed a huge snacking culture here in America and I wonder if the interpretation of research on this subject has turned us into hyper-snackers and we never let our bodies draw from our fat stores for energy because we're so busy snacking. Then we wonder why we're not losing fat.

However, I do think eating fewer than three times a day is a bad idea. Skipping meals may not be as metabolically devastating as people think, but you are way more likely to binge at the next meal if you've gone for hours and hours without eating.

I recently checked a book out from the library on metabolism. It was by some 'celebrity nutritionist.' She was a big one for frequent eating. She said you should even eat right before you go to bed, which struck me as pretty ridiculous. Why eat right before going to bed? Yeah, you're really going to be burning it up in your sleep. I don't know, maybe I just didn't like her because she told me to give up coffee. But really, I thought her book was ridiculous. I don't even remember her name or the title, just that she bandied about the names of all the famous people who seek out her fabulous guidance. Basically, she was recommending a low calorie diet spread out throughout out the day... and evening. If her plan works, I'm thinking it's just because it was low-calorie, not because of the bedtime snack.

Alright, I need to go feed the small people (and myself) but I have a lot more to say about metabolism. Next time we'll discuss how to exercise to maximize metabolism. I know this wasn't the most knee-slapping post ever, but it's a little hard to make metabolism funny. While metabolism is interesting, it's also a little boring, you know?

In the meantime, I'd love to hear your thoughts about frequent eating. Are you a snacker or more of a three squares a day person? Do tell!


  1. I'm a semi-snacker. I definitely need an afternoon snack to get me to dinner, otherwise I do tend to overdo my portions. I sometimes do need a before-bed snack too. Front-loading calories (eating more earlier in the day) helps keep me from getting hungry in the evening, but there have been times (e.g. while pregnant, while training for a 10K) when I just couldn't get enough in me. And I can't go to bed really hungry! I just lie there thinking about food.

    Controlling ALL my portions is a bit of a battle, but does seem to be the key. And those BMR calculators just baffle me. I am relatively petite, and therefore burn VERY few calories during the day. So running 10K adds about 50% to my total. Insanity!

  2. Pratima, I wouldn't put too much stock in those online calculators. They don't take muscle mass, heredity and many other factors into account when figuring the calculations (obviously.) I think they just give you a ballpark figure, esp. for very fit people.

    And I'd certainly agree that pregnancy and endurance sports put you in a different category!

  3. Great article. And yes, the Bob The Builder metaphor really helped me. Motherhood has worn my education down to the preschool nub. ;)

    I thought I was a frequent meal eater but that changed, along with everything else, when I relocated back to the South. In NYC I ate frequently because I burned up every calorie I consumed, especially when I started Project You. I was literally eating every hour. When I returned South frequent meals lead to weight gain because I wasn't burning anywhere near the same amount of calories. I worked in a somewhat smaller building, I drove instead of walked and the lifestyle pace is noticeably slower. Once I figured that out I resumed eating 3 squares and perhaps an afternoon snack with relatively easy daily exercise and the pudge finally budged.

    1. Hmmm... interesting. Def. supports what I've been reading! And 'preschool nub.' love it. :)

  4. I used to be a long-distance runner, and I pretty much ate what I wanted (yay!) and just went for long runs (also yay!) and didn't worry too much about my weight, and it was all fine. Sadly, I am now coming to terms with a post-two-pregnancies body, and a distinct lack of time in my weekly schedule to do anything resembling marathon training. Pilates and Zumba keep me relatively sane and happy, and muscles and joints all functioning, etc, but that darn metabolism is slowing down. And the post-baby weight hasn't quite gone. Sometimes getting old just sucks!

    1. Sane, happy and joints functioning--sounds like you're doing great! We'll just get you some more muscle and that will help with the metabolism. But really, if you're sane, happy and can bend your limbs, that's all good stuff!