Many people blame their expanding waistlines on a slow metabolism. But is that really what's keeping you from reaching your ideal body composition?
What is Metabolism?
Metabolism is your body's method of converting calories, from the food you eat, into energy needed to power all the physiological processes that keep you alive and kicking 24/7. The minimum amount of energy your body needs to keep you going is called Base Metabolic Rate (BMR).
Calories in food - protein, fat and carbohydrates - fuel your BMR. Each of us requires a unique daily number of calories to maintain BMR so we can breathe, grow, think, sleep, digest food, and filter waste. Age and lifestyle are significant factors in calculating BMR. If you sit more than you move each day, your BMR is lower and your daily calorie needs are lower, too.
Calories In, Calories Out - Not the Whole Story
Losing or gaining weight is not just about energy balance (calories taken in - calories burned off). Sure, if you take in more calories than your body needs you'll probably gain weight, but it's not that simple. The food we eat acts as a chemical messenger that tells our hormones and other chemical compounds in our bodies what to do.
I always give the example of the doughnut and the chicken breast: both have about the same calories but the chemical reactions that occur on the body after ingesting each of the foods is drastically different. The combination of fat and starch in the doughnut will cause your blood sugar to spike and ghrelin, often called the "hunger hormone". So in short, the donut puts your body into fat storage mode, increases hunger and promotes insulin resistance.
The chicken breast on the other hand stimulates production of glucagon which enables the body to burn fat instead of storing it when insulin levels are low. The protein in the chicken also stimulates leptin production which helps suppress hunger. This is why most people could eat several doughnuts but would struggle to eat more than 1 or 2 chicken breasts.
Here's a great excerpt from this article by Dr. Keoni Teta that helps explain the importance of hormones in relation to body composition:
GLP (glucagon-like peptide) and GIP (glucose dependent insulinotropic peptide) are secreted by the endocrine cells of the small intestine. They basically help the body sense the macronutrient ratio the incoming food. In other words, they taste the food in the small intestine and tell the body whether there is more fat and sugar in the meal or more lean protein and vegetables in the meal. More fat and sugar in the meal cause the small intestine to release more GIP relative to GLP, and the more protein and fiber in the meal causes release of more GLP relative to GIP. Think of GIP as fat storer and GLP as fat burner.
Eating more protein and vegetables influences a stronger signal of GLP relative to GIP thus helping to burn fat.
Your Genes are Not Your Destiny
Your genes (and hormones) play a role in metabolism because they can influence the potential you have to grow muscles (how dense and how big) and how your body stores fat. However, genetic and hormonal mechanisms in metabolism are extremely complex. There are no definitive theories. Yet, many people have lost and maintained a tremendous amount of weight despite their family history. Many health experts agree, "Your genes are not your fate."
Chances are your 'slow metabolism' has more to do with your diet and the type of exercise you are (or are not) doing on a regular basis.
If your exercise routine builds lean muscle, that helps rev-up your metabolism. Muscle tissue requires more energy to maintain than fat tissue. This is why people with leaner bodies (a higher muscle to fat ratio) have a higher BMR. (Those are the folks who eat carrot cake that doesn't 'go right to their hips.)
Build a 24-Hour Fat Burning Body
The first key to revving-up metabolism is eating a whole foods diet: clean protein (organic, pasture-raised meats and poultry and wild seafood), anti-inflammatory fats and oils, fresh organic fruits and veggies, and drinking lots of water.
To really turn-up the heat on your metabolism, and your waistline, you'll want to try the muscle-building, never boring workouts listed below. These workouts help your body generate a 'post-exercise burn' that can rev up your metabolism for 2 - 24 hours after you finish a workout. Factors that determine the "afterburn" effect include your current fitness level and body composition, the intensity and duration of exercise, and type of exercise performed.
Just remember: Our bodies are designed to adapt; beginners to elite athletes both have to change-up their routine every few weeks to continue to see progress.
Circuit Training: Exercises all the major muscle groups in one workout (30-45 minutes) and may include body-weight movements, machines, dumbbells, and exercise bands. Exercises are performed for 8-12 reps, 1-3 sets of each.
High-Intensity Interval Training (HIIT) and Rest-Based Training. These workouts alternate bouts of maximal physical effort with a rest (or lower intensity) period for set times (e.g., 40 seconds max, 15 seconds lower effort). HIIT principles can be integrated into a variety of exercise routines including walk/run, swim, weight training, and group classes. Research shows an increase in calorie burn for up to 24-hours post exercise. I take this a step further with what we Metabolic Effect folks call "Rest-Based Training". This means that you go as hard as you possibly can during a high intensity interval until you have to rest. You then rest as long as you need to until you can go again at the same intensity. This allows you to individualize a workout to your fitness level and achieve that afterburn effect in less time.
Metabolic Conditioning routines are highly intense and designed to engage different physiological "energy" pathways in the body. These workouts typically use a "suspension exercise system" (e.g., TRX) but can be integrated into other fitness activities. It's best to have a metabolic exercise routine designed and supervised by an experienced exercise specialist who can appropriately alter the intensity, reps, sets and rest intervals.