Burn Baby Burn

Quick Notes on Energy Expenditure and What it Means for Weight Loss

By Catherine Munaco

Owner, CoachMeFit West Bloomfield

As a trainer, I have one basic rule for clients aiming to lose significant amounts of weight: You must know roughly how many calories you consume relative to how many calories your body is burning on a daily basis. Surprisingly, very few people have looked into their energy consumption and expenditure, and instead take what we call “uneducated guesses”. As humans, we tend to underestimate the calories in our food and overestimate the energy we use during our daily routines and workouts. Clients are often reluctant to spend time tediously logging entries into a food diary, and even nutritionists will say that calculating calories in food is a time consuming process. I simply don’t care. I’ve logged my food consumption, its annoying—yes—but vital, read: VITAL, to progress with weight loss. Luckily, online food journals make tracking easier and less time consuming than it used to be (try fitday.com for a free online food journal). If tracking food every day isn’t something you’re likely to stick with, then track for three days (making sure one of those days is on the weekend). Because we tend to be creatures of habit, you’ll get a general idea of how many calories you eat in a typical day. Most likely you’ll be shocked with the amount of calories you’re consuming. If you eat out, be sure to look up calories on the restaurants website, which can also be shocking. I’ll never forget when I learned that my “healthy” Panera salad contained over 30 grams of fat. Simply substituting the dressing would have saved me over 200 calories.

The other half of the equation, of course, is calories expended. Here, we also see inaccurate guesses. Clients will often tell me they went for a long walk, but when I put them on the treadmill they realize how slow they were really moving. For a more accurate calorie count, I usually suggest a heart rate monitor. Cardio machines typically have a spot for calories burned in a workout session, but even they can overestimate. One time, the treadmill said I burned 800 calories in a 40 minute run; my heart rate monitor said 425. (I would have loved to believe the treadmill, of course, but a female my size would have to run faster than 6 minute miles to expend that much energy in 40 minutes, and I don’t think I’ve ever run a 5:50 minute mile, let alone 8 of them.)

Additionally, my clients usually have no idea how many calories they use at rest. The most simplistic estimation of this value is what exercise physiologists refer to as resting metabolic rate, or RMR. RMR accounts for the energy required by cells to maintain normal bodily functions and homeostasis at rest. Similar to RMR, basal metabolic rate, or BMR, is the minimum energy needed to sustain vital life functions. In laboratory conditions, BMR is typically only slightly less than RMR, so the two tend to be considered interchangeable. Regardless, knowing your daily BMR or RMR is crucial to weight loss. Again, people are often shocked to learn how little they burn at rest. Equally frustrating—BMR is lower in females (a result of lower muscle masses as compared to males) and decreases with age. To calculate your age, gender, and weight adjusted BMR, go to http://www.bmi-calculator.net/bmr-calculator/

Aside from physical activity and exercise, BMR ends up being the most important form of calorie expenditure simply because we spend most of our day at rest. Having a basic understanding of our daily energy needs allows us to regulate and change the foods we eat to better accommodate energy expenditure. In the long run, we want eating HABITS that fit our energy needs. Knowing BMR also highlights the importance of physical activity. On days that we put in a significant workout, our caloric expenditure is as much as 25% greater than our resting levels. That means we can eat more! Exercise increases weight loss when calories are carefully monitored and helps to buffer “bad eating” days (you know you’ve had ‘em).

Research has also shown that exercise can have a counter effect on the natural decrease in BMR with age. Age-related decreases in BMR are typically explained by loss of muscle tissue and increase in fat tissue. Some changes in metabolic activity for muscle also exist as we age, but for the most part we lose active muscle tissue, and therefore burn less calories at rest. However, weight training can help maintain muscle mass that we would otherwise lose, thus keeping basal metabolic rates from plummeting. Some research has even suggested that regular aerobic training in older individuals causes increases in BMR with no increase in muscle mass.

BMR often decreases with age

BMR often decreases with age

So what does this mean for the average person? It means that you need to keep moving and you need to know what you’re consuming relative to what you’re eating. Weight loss only occurs when energy out is greater than energy in, but if we don’t at least have some general idea of what our individual caloric consumption and usage is, we can’t begin to know what to change to see results. Is it a pain in the butt? For some of us, yes. Is it necessary? YES. Fitness is a lifestyle, not a temporary fix. Knowing what your body is doing is the first step to changing habits and creating new patterns for a lifetime of health and wellbeing. Smaller pant sizes are the satisfying bonus.

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