The basics of metabolism say that as long as we burn more calories than we consume, we should lose weight. The opposite is true for gaining weight. So why does it seem like there is a lot more to this simple scientific principle? Well it turns out that counting calories is more inaccurate than you think, can take up lot of time, and even if you have the mental resolve to weigh out and calculate everything that you eat, you may still be getting it wrong. There are many different factors that affect calorie estimates not to mention that we are all unique to start with.
Let us start with one of the most common issues that arise when trying to figure out just how many calories are going into our bodies, nutrition labels. Nutrition labels are on most prepared food in Canada and break down a food’s nutrient content, as well as calories. We can use these labels as a guide to decide what foods to eat but the nutrient and caloric content can be up to 20% inaccurate, by law. Therefore, a 2,500 calorie diet could actually be more like 3,000 calories! You would need to do an hour of rowing to burn off that extra 500 calories. Not only can the data we use be inaccurate, it can be outdated as well. The method used to measure energy stored in food (aka calories) is more than 100 years old and much of that data is still in use today. Think about how food has changed in the past 10 years let alone the last 100! We have gone from small-scale farms to massive GMO farms and greenhouses; do you really think our food is the same? Furthermore, one of the hardest parts of counting calories is simply weighing and measuring EVERYTHING, so most of us just eyeball portions instead and by doing so we end up eating much more than we think. A little bit extra here and there can turn into a few hundred calories more per meal and thousands more calories per week.
What happens when we factor in our own biology, like digestion? In a lab, calories in food are determined with a machine that burns a food sample to see how much energy or calories are in a food. Unfortunately, our bodies do not break down food nearly as much as a machine in a lab does. Some foods pass through our body undigested, while at other times our body simply does not absorb all the nutrients and calories in our food. Typically, our body absorbs about 4 calories per gram of protein and/or carbohydrate and about 9 calories per gram of fat but nuts, seeds, and even fiber rich foods do not follow this formula. The chemical makeup of food itself can even dictate the amount of calories we burn. In fact, it takes more energy to break down protein than any other macronutrient… This is why we sweat when eating a lot of meat (protein) and is also why people think eating spicy foods will help to burn more calories, although, this doesn’t give us an excuse to eat hot wings everyday! Even cooking food can add more calories! Raw eggs are about 50 calories while cooked eggs are about 75 calories, and baking a potato can add almost 100 more calories. Even the oils and butters we use in cooking can add extra calories.
Trying to count calories is starting to look like a lot of guesswork; what about figuring out how many calories we burn? Again, there is a lot of acceptable error and individual variability involved. Fitness trackers have been popular for years and while they are getting more accurate, (they now measure things like heart rate… not just steps) but they still only give us a rough estimate of how many calories we may have burned, with an accepted error of around 30%. Our height and weight can play a large role in how hard we work to move or exercise. There is simply no perfect way to tell how many calories we have burned! There are also many other physical variables that also affect how many calories we burn. People with higher amounts of certain gut bacterium will burn more calories compared to those with lower amounts. As we age, our body’s metabolism slows down meaning we have to work harder just to burn the same amount of calories as we did in our youth. Our hormones can affect metabolism and even getting enough sleep can dictate how our bodies use stored calories. Overall, it is not unusual for someone’s metabolism to vary by up to 100 calories a day difference.
A history of being overweight or obese may actually slow down metabolism, as the body will try to maintain its previous weight as we start to lose weight; so we may need to restrict calorie intake more or work a little harder to continue to lose weight. Be careful though, restrictive dieting may work in the short term but in the long term the result is often the opposite of what we want. This is why yo-yo dieting can be problematic and why we have all heard someone say the first 10 pounds lost is not the same as the last 10 pounds lost.
So if counting calories is nearly impossible to do correctly; then how do know if we are on the right track? Firstly, we can still use calorie estimates to give us an idea of how much food we should be eating or how much exercise we need to do. From there it is a matter of testing and adjusting our lifestyle to match our goals. If you do not see changes or things are going the wrong way after a few weeks, then modify one thing and re-test, maybe change your food or portion size, or change your activity levels. Of course, we need to be consistent and eat a variety of mostly whole unprocessed foods, as well.
It is so easy to overeat! Small manageable changes, while often slower than big changes, offer the healthiest and most sustainable form of weight management.
Paul Bradshaw l Kinesiologist