Many perceive the metabolism to be much like a spirit that inhabits the young body and then decides to vanish into the ethos as we age. Many believe certain things will make this spirit stick around longer, like eating every 30 minutes, and praying. Parallel with these beliefs is the idea that one can boost or vanquish their metabolism with one wonderful or terrible decision. I am here to throw a sheet over this metabolism poltergeist.
Metabolism is the sum of reactions that take place to build up and break down the body. Metabolism happens on a cellular level, which is why it seems so far out of our control, how can we control trillions of tiny cells? Some aspects of metabolism are more auto-regulated than others, yet our actions do affect our metabolism. Understanding these actions and the pieces that make up metabolism will put us back in the driver's seat. Metabolism can be broken down into 5 components: Basal Metabolic Rate, Resting Metabolic Rate, Thermic Effect of Feeding, Exercise Activity, Non-Exercise Activity Thermogenesis.
Basal Metabolic Rate
BMR is the minimum level of energy expenditure needed to maintain vital functions in the body. This means the minimum amount of calories needed to keep us alive in a fasted state. Think of BMR as your baseline metabolism. Here goes a typical body-as-house metaphor: BMR is the electricity bill when you first get a new house. The lights haven't been used, but you have enough electricity to use them. BMR doesn't include your gas bill (digesting food).
70% of the calories we burn on a daily basis are used for BMR, to keep our vital functions functioning. This is is the part of metabolism that we have the least control over. Not to fear, the other 30(ish)% of daily metabolism is highly variable and within our control.
Resting Metabolic Rate
RMR is very similar to BMR. It is The amount of calories needed to sustain the vital functions at rest. In layman's terms, RMR is BMR with more lax testing standards. RMR is usually only 10% higher than BMR. Testing for BMR requires the test subject to be in a fasted state and sleep 8 hours in a temperature regulated room (my mom would be a great candidate, hi mom). RMR test subjects are allowed to eat and move, but not perform strenuous activities. RMR formulas are based off an organism's lean body mass. LBM (think muscle) is more metabolically active than fat, meaning it burns more calories at rest than fat. This is why strength training is important, if you have more muscle, you will burn more calories at rest.
Thermic Effect of Feeding
TEF is the amount of calories needed to digest food and distribute nutrients into the blood. This is where the 'eating more frequently boosts metabolism' idea comes from. Eating food does burn calories, but not enough calories to cancel out the food you have just eaten. When you don't eat, your body will not be using calories to digest food, and when you do eat, it will. So, yes, your metabolism is lower without TEF, but so is the amount of calories you have taken in. The second you eat, TEF gets kicked into gear. Eating more frequently isn't like a fire that keeps your metabolism going, it is like a fire that burns the kindling you need to light it with. Proteins require the most energy to break them down, and fats need the least. TEF accounts for about 10% of daily metabolism.
Exercise Activity
The calories burned to perform exercise are a highly variable component of daily energy expenditure. Exercise activity can account for 10-30% of daily metabolism depending on an individual's activity level. The more strenuous the exercise, the higher its metabolic demand. When an individual does steady state cardio (like running or cycling), the metabolic demand will only occur during the period of exercise. Strength and power training (weightlifting, lifting weights) creates such a high metabolic demand that the body has to play 'catch up' and remains in a metabolically elevated state after the exercise is completed.
Non-Exercise Activity Thermogenesis
NEAT is unplanned, low intensity physical activity that takes place every day. NEAT includes walking, pacing, doing chores, fidgeting, etc. NEAT is a very important component of metabolism. NEAT happens almost automatically, yet its effects are undoubtedly noticed.
When an individual (let's call him Bob) undereats his body will adjust by decreasing his NEAT. Maybe Bob used to fidget and pace; now underfed, this extra movement will cease. When Bob goes back to eating regularly, he will subconsciously be in the habit of conserving energy. With NEAT accounting for fewer calories than he is now taking in, Bob will be an example of someone who thinks he ruined his metabolism on a crash diet.
Conversely, I have many clients who increase their NEAT by walking a bit more each day. This may mean getting out of the train one stop early, pacing or standing at work. This seemingly nominal amount of activity pays off in divedens. One can boost their daily metabolism by a few hundred calories by increasing NEAT. NEAT is really neat, anyone can do it quite painlessly and it really does aid fat loss. I do not have one client who it has not helped.
Ghost busted?
Metabolism is an ever-changing, open ended process responsible for keeping us running and keeping us from running on empty.
Here are the top ways to 'boost' your metabolism:
• Increase your lean mass. Lean tissue burns more calories than fat. The majority of age related 'metabolic decline' is based on muscle loss.
• Eat about every 3 hours
• Eat protein with every meal
• Strength train at least 3x per week
• Increase NEAT!
Know that you have almost total control over your metabolism. You aren't stuck with a slow metabolism, it is your lifestyle choices that are slowing it down.
