Losing Weight

Transcript

Most people think they know their bodies pretty well. They think they know their cars, too, but we readily admit that for the actual details, we’re often pretty clueless. Unless we’ve recently changed one, many of us don’t know what size our tires are, but we’re okay with that. When it comes to our selves, though, we like to pretend we know everything. Let’s take a look at some of those details that people often think they know, and explain how tiny choices work together to become the you that you are.

The first thing we should tackle when talking about the body, is to explain exactly what we mean when we say metabolism. You’ve probably heard the number 2000 calories before, particularly on the sides of cereal boxes and other nutritional labels. Where did 2000 calories come from? In 1990, the FDA took a survey and asked people how many calories they ate, and published the average, as a baseline. It’s helpful to translate that 2000 calories into an example. 2000 calories is roughly the amount of calories needed by a 5’9 man, at 200 lbs, in a coma to avoid losing weight. That’s his basal metabolic rate, the minimum amount of calories to simply sustain muscle mass and bodily functions with no energy exerted.

We can calculate and estimated basal metabolic rate, or BMR, using this equation, using height, weight, and age. These are just estimates, and physical fitness does play a part. It’s often easier to us an online calculator, like the one linked in the lesson, to determine our BMR. After we know our “coma” energy level, research done in 1918 gives us a way to estimate what our energy needs to be to maintain a lifestyle we want to maintain. We take our BMR, and multiply it by factors determined by J. Arthur Harris and Francis G. Benedict called the Harris Benedict equation.

Simply being awake a normal amount of time and occasionally moving from bed to couch multiplies your BMR by 1.2, so our 5’9 200lbs man needs 2400 calories to wake up and watch tv all day without eventually wearing down or losing weight. A slow walk a couple times a week increases his BMR 1.37, or up to 2750. That’s a daily increase, not simply the results of his exercise plus his BMR. When activity takes place, besides the simple exertion of whatever actions are being taken, fluids and minerals are being moved all over the body. Harris and Benedict measured the additional heat created by the bodies rebalancing of those fluids and minerals, which includes things like the kidneys and liver filtering blood, sugars and proteins being moved in and out of cells, and water being balanced across the body, and determined that the effects of exercise on our metabolism are slow cycles that play out over several days. The older you get, the more obvious of a statement this is to many adults.

To understand the Harris Benedict Equation, it’s important to realize two things that have been repeatedly confirmed in peer reviewed studies. The first is that exercise really means activities that raise your heart rate to around 70% of your maximal heart rate, and keeping it around that range for only about 10 to 15 minutes. For most people, a brisk walk will accomplish sufficient exercise to move them into the “moderately active” range, but many people still think of themselves as sedentary.

The second thing to notice is that the benefits of exercise fall off somewhat rapidly. Moderate walking will get you to almost as much benefit as daily weight lifting, in terms of resting metabolic rate.

Knowing this, we can now figure out how many calories we currently need. We figure out our BMR from the online calculator, and then estimate how active our life is. If that 5’9, 200lbs man wants to walk briskly for 10 minutes every day, and do an hour or two of yardwork every weekend, he can consider himself moderately active, and he needs around 3000 calories per day in order to maintain his weight and activity level.

What happens if he doesn’t? He’ll eventually lose weight. Our society likes to use that simple phrase as if it describes what’s going on in the body. It’s a very simple description of what’s happening. Let’s take a look at the cycles that control what really happens. In Western culture, we tend to think of the body spending energy in a few specific ways. The Energy to Move and the Energy to Digest. However, as we’ve already mentioned, the BMR is already a fairly large part of your energy consumption. Most of what takes energy in the body is the movement of molecules in and out of cells. The active expenditure of energy to balance a cell to perform its function burns a substantial amount of energy. When you run out of energy, it’s easy to think only of losing the ability to run and jump, but it’s also the healing within a cell that becomes lost eventually. The body has many mechanisms that kick into action to respond to this loss of energy. What happens next in the body depends on what fuel the body has been able to digest recently.

You have no doubt heard about the three macronutrients, protein, carbohydrates, and fats. In a given day, to heal and reproduce cells, the body needs a relatively small amount of amino acids to repair any damage done to the body and basic bodily repair and upkeep. It also needs a lot of water to replace fluids lost during exercise and respiration, as well as for digestion, and to flush out waste products with the kidneys. In order to heal cells, you need to have at least that amount of amino acids and calories available, which we can loosely think of as our blood sugar level. A simplified version of how to think of it is that our cells have calories in them, or can suck calories in from the blood, while our pancreas works to ensure the calorie level in the blood stays at the same rate.

When the level of blood sugar is too high, it tells the body to store the calories from the blood. It doesn’t tell your body to get fat, it tells ALL the cells to absorb sugar, and if your cells aren’t hungry, the fat cells are where the sugar gets absorbed. When the blood sugar is too low, it tells the liver to release stored sugar.

Although most of that cycle is essentially automatic, and oddly enough, burns only a small amount of calories. For example, vigorous weight lifting may only burn 250 calories in a large man in a half hour. That’s a Snicker’s bar worth of energy. The processes of replacing those calories in cells and rebuilding any damaged muscles is what causes your overall metabolism to rise according to the modifiers in the Harris Benedict equation.

In response to exercise, the body undergoes an adaptation process in many ways, from increasing muscle mass, to expanding blood vessels and creating more capillaries. The body must also rebalance fluids, redistribute nutrients, and digest the increased nutrients. All of these things factor into the increase in metabolic rate in response to exercise besides the physical demands of the activity.

Remember, everything that’s happening in the body is the result of a chemical reaction that’s happening right at that moment. The body has a very limited ability to store protein, and must break down muscular tissue to produce the amino acids necessary to repair or create other tissue. In order to build or maintain muscle, you must always consume enough protein at regular intervals to continue this energy expenditure.