Wikipedia states that it “is the set of life-sustaining chemical transformations within the cells of a living organism”. A more common definition would include how our body uses calories to gain, maintain, or lose weight, along with digestion and absorption of nutrients.
It is important to note that metabolism is not a static thing that exists in some specific area of the body. Rather, it is a means for the body to regulate its own existence and ensure its survival.
A common misconception is that our metabolism will stay constant and we can merely decrease calories to lose weight or increase calories to gain weight. Although this may work for a time, ultimately, the body will alter its metabolism to adjust to the changes.
I see this most common with individuals trying to lose weight. They drop calories significantly, for such a long period of time, with no return to healthy intake levels that a “starvation response” ensues. The body panics and slows its metabolism, making the new calorie intake level its maintenance level, thereby preventing further weight loss.
This same process occurs if someone is over-training. Their body adjusts to the stimulus. Their central nervous system becomes overwhelmed from fueling workouts with adrenaline. The body holds onto weight to ensure self-preservation. And it even sacrifices functions of health regulatory systems, such as the immune system.
Hence most exercisers or dieters will lose a few pounds the first few weeks but pretty quickly plateau.
This also happens if an individual is consuming excess calories to gain weight. If they eat more calories, more frequently, metabolism will increase. Also, the body temperature will rise in an attempt to burn the extra calories.
The body is a highly adaptive system and life has one overarching goal – to maintain its existence and proliferation. Drastic changes, whether weight gain or weight loss, cannot always be caused by simply picking a new caloric intake level. They require a dynamic way of structuring activity and nutrition to convince the body to work towards the changes you want.
Another issue that many people overlook when discussing metabolism, is the thermic effect of different foods.
Every macronutrient (fats, carbs, and proteins) requires different levels of energy from the body to be processed internally.
About 30% of the calories from protein are used during digestion alone. About 10% of the calories from carbohydrates are used to process and store them as fuel. And about 5% of the calories from fat are burned during processing.
To simplify this, if you eat 100 calories of chicken, your body is only netting about 70 calories. If you eat 100 calories of rice, you are ingesting 90 calories. Eating 100 calories of olive oil will result in about 95 calories.
This is one reason so many people experience easy weight loss when they focus on consuming enough protein – their body is naturally burning more calories before it even has a chance to put the protein to use. Also, protein will be far more filling, thus eliminating cravings caused by high carbohydrate consumption.
The most effective way to lose fat or gain muscle would be to structure caloric intake in a step-like fashion.
Let’s assume an individual needs 2,000 a day calories to maintain their weight.
Maybe for two weeks they shoot for 1,700 – 1,800 calories a day. The next two weeks they drop to 1,500 – 1,700 calories a day. Then on the fifth work, return to your maintenance level around 2,000 calories a day. Repeat this cycle, recalculating maintenance calories every 5 – 10 lbs, until you reach your goal.
During this process, feel free to step on the scale, at the same time of day and same day of the week, and note changes on a weekly basis. Shoot for half a pound of fat loss a week…although one pound will be manageable for individuals that have more to lose.
To be honest, I’m not actually an enormous fan of the weighing and measuring approach. I find it develops certain neurosis and an obsession with arbitrary numbers. If you performance is improving, your blood work is good, and your clothes fit better, the specific numbers on a scale or calories on a plate are irrelevant.
This way of structuring caloric intake is similar to the theory of periodization in training. Over the course of a few weeks or months, slowly increase the intensity before taking a recovery week, allowing the mind and body to prepare for another period of improvement.
Track your progress, make changes if things stagnate, or stay the course if you are succeeding.
So, if you’ve been consuming 800 calories for months, and wonder why you’re not losing weight, it may be that your metabolic rate has decreased.
Take a few weeks of eating at maintenance to allow your metabolism to reset, and then give this calorie cycling a try!