What is a calorie?
A calorie, as we often see it on a nutrition label, is actually a kilocalorie. To make it simple for consumers, it became a Calorie with a capital C, and since then has been used so often without the capital C that we just use calorie. The true Calorie, or kilocalorie, is a measure of the energy required to raise one kilogram of water one degree Celsius. Originally, the calorie value of a food was determined by burning it, but today an assumption is made based on the protein, carbohydrate, fat and alcohol content of a food. These values are rounded according to the following table:
Again, these numbers are not exact. One of the reasons they’re not precise is because a certain amount of energy is required to break down and absorb these macronutrients. After accounting for the energy expended, a gram of protein provides about 3.2 calories, a gram of fat 8.7 calories and a gram of carbohydrate, 3.8 calories. These numbers are not exact either, because different forms of each of these macronutrients require varying levels of energy for digestion.
The 3500 Calorie “Rule”
If you did not see all the estimates in the past few paragraphs, read them over again. Even if the “calories in, calories out” concept worked, the math wouldn’t work because there are so many variables involved.
Counting Calories In
This becomes even more complicated when you consider the variability of the foods we eat. A piece of grass-fed beef usually has less fat by weight than the same cut from a conventionally raised cow. If it has less fat by weight, it will have more protein. For the same 8-ounce piece of meat, it would have less fat and more protein, and fewer total calories. How much less? You can’t be sure, unless you actually test the meat. But then you wouldn’t be able to eat it, so you’d need to get another cut of beef that wouldn’t be exactly the same, so you wouldn’t know the calorie value of that piece of meat either.
Let’s pause here for a moment. If you were truly going to gain an extra pound of fat by eating 3500 calories more than you burn, you’d only need to eat 116.66 calories per day more than you burn in a 30-day month to gain a pound of fat. That’s 38.88 calories per meal if you eat three meals per day. Even if you weighed and measured every bite of food you put in your mouth, you’d still never be able to manage your calorie intake accurately enough because the whole idea of the 3500 calories and the calorie value of the macronutrients are based on so many assumptions and rounding of numbers!
Remember, the calorie balance equation assumes that you must maintain a precise balance between the number of calories you consume and the number you burn. If the calorie balance equation were true, and you eat 38.88 calories per meal too many, you’ll gain twelve pounds of fat per year. How can you get to precision of 38.88 calories when everything above is based on so many assumptions and rounding of numbers?
Counting Calories Out
Resting metabolic rate is the energy the body requires just to maintain normal function, tissue repair and keep you breathing while at rest. Resting metabolic rate makes up the majority of energy the body burns during the day and can be easily tested through a resting metabolic assessment. When one’s metabolic rate is higher or lower than normal, it can be an indicator of metabolic dysfunction. The body also tends to increase its metabolic rate when it gets enough calories and nutrients, when under acute stress or if recovering from trauma like an injury or an intense workout. It lowers metabolic rate when energy is restricted, such as a typical low-calorie diet, or when under chronic stress.
You also have the Thermic Effect of Food (TEF) which is the percentage of a food’s calories burned in the process of digestion. Our bodies burn a certain amount of calories just breaking down our foods and rearranging them in a way we can use for growth, repair and energy. The TEF for protein is 20 to 35 percent, meaning that up to 35 percent of the calorie value of protein will be burned just to digest that protein. Compare that with the TEF of carbohydrate at 5 to 15 percent and with fat being the same or less than carbohydrate. Increasing the amount of protein in the diet, while keeping the total calorie value the same, means fewer calories will be available for energy or weight gain.
Exercise is another way calories are expended during the day. Workouts are a very minor part of the total calorie expenditure for the average person. Professional athletes train for hours every day, but for most of us, our exercise sessions last about an hour, three to six times per week. The number of calories one burns in an exercise session is not important. What’s interesting is that research has shown, those who burn the most calories during an exercise session also have the strongest appetite later in the day, or they feel the most worn out. The body knows it should save some energy later in the day, or eat more, to compensate for the demanding training session. I’ve also seen this from personal experience in working with people.
Exercise, or training sessions, should be designed in a way that improves range of motion, increases coordination, stimulates the growth of muscle tissue, or helps your body become more efficient at using fat for fuel. Each of those four goals improves one’s health, metabolism, performance or endurance. If the goal is simply to burn as many calories as possible, it can lead to workouts that increase cortisol, the body’s main stress hormone. These high-intensity exercise sessions also drive cravings for sugary foods or decreases activity the rest of the day. The increased appetite or fatigue are ways for the body to help maintain glucose levels. Interestingly, when people train at an intensity level that allows them to use more fat for fuel, rather than carbohydrates, cravings are not nearly as significant and they are less likely to feel so fatigued afterwards.
If the “calories in” side of the equation could be accurately measured (we already said it can’t), what is the likelihood we could precisely account for the energy we expend each day? It would also be nearly impossible.
Starving While Being Overweight
Most of the research showing how metabolic rate slows down has been done with individuals following a mixed diet, higher in carbohydrates, lower in fat and low to moderate in protein. The hormonal effects of a diet dominated by carbohydrate consumption are quite different than a diet with lower levels of carbohydrate.
Carbohydrate is often called “quick energy,” but it’s not because you actually feel energetic after consuming it (though many sports drinks would like you to believe that). The reason it’s called quick energy is that it’s available as a fuel shortly after consuming it. When sugars hit the blood stream, the body quickly shifts from burning fat to burning sugar. If it’s burning sugar, it can’t burn fat. The one exception to this rule would be fructose, which is sent directly to the liver and most of it is converted to glycerol, which helps to create triglycerides.[i]
Whether the body perceives a shortage of available energy is determined by the type of diet an individual follows more than the amount of calories in the diet. As you will see below, an overweight individual may have a metabolism that thinks it’s starving, simply because it cannot access the tens of thousands of calories worth of energy stored in its fat cells.
Low-fat, low-calorie diets
Her focus is on getting the most enjoyment out of the limited number of calories she can eat each day, so she resorts to a variety of pre-packaged, low-fat foods like cereal, low-calorie juice, snack packs, some fruit, and other whole grain foods. If she’s a little more in tune with what her body needs, she’ll also sneak in some low-fat or fat-free protein like chicken breasts, non-fat yogurt or fat-free cheese.
Because the majority of the foods in her diet come from carbohydrates, her insulin levels remain elevated throughout the day. When insulin is high, fat cells cannot release their stored fatty acids for energy. Instead, the body uses whatever glucose it can from the blood stream or what’s stored in the liver as glycogen. When the glucose levels get used up, hunger strikes and Julie will be looking for another high-carb, low-fat snack to curb her appetite.
In this scenario, even though Julie’s calorie levels are low, and she should be burning more calories than she eats, she still can’t access her extra fat. Without access to the stored fat for energy, the body responds by stimulating hunger and lowering metabolic rate. If it doesn’t have access to energy, it will respond by burning less energy. Though her body is a “rich” source of energy from all the fat it has stored up, it’s almost useless since Julie spends most of her day eating foods that limit the ability of her fat cells to release the stored fat.
If you were to put numbers to it, Julie probably burns 2500 calories per day. If she’s eating 1400 calories per day it leaves her in an 1100 calorie deficit. In six months’ time, she should lose about 53 pounds. In reality, she’ll probably lose about 20 and then get stuck. Unless she does something different with her nutrition, or exercises even more, weight loss will slow down because her metabolic rate will adjust to the fact that it doesn’t have available fat to burn.
With a reduced metabolic rate and constant hunger, it’s little wonder why people who follow this common approach have little success long-term.
A second approach is to follow a nutrition plan that doesn’t focus on managing a calorie level, but instead focuses on optimizing the body’s ability to burn fat. The body is able to burn fat when insulin levels are low. Eating fat has no effect on insulin, and protein has a very small effect. That’s why we encourage people to base their diet on non-starchy vegetables, high-quality protein sources and healthy fats. That’s also why reduced-carbohydrate diets have been shown to be more effective for fat loss than low-fat diets. In fact, they’ve been shown to be more effective for fat loss even when the low-fat groups are on a set calorie intake and the low-carb dieters are allowed to eat as much as they want to.
The average person has tens of thousands of stored fat calories. When the body is able to access them, metabolic rate is less likely to fall, even if they’re eating a lesser number of calories. When they eat an excessive number of calories, but still don’t eat enough carbohydrates to raise insulin, they may not lose weight, but they’ll have a more difficult time gaining weight. Without insulin, the body doesn’t get a signal to “store” calories. Instead, the body may respond to extra calorie intake by raising metabolic rate further, or by wasting the extra calories through heat.
To answer the question that started this section, weight is lost when the body is able to release fat from the fat cells, and when there is a need to burn it as fuel. If the fat is trapped in the fat cells because of the diet one follows, weight may be lost, but it won’t necessarily be fat. Instead, muscle will be broken down to supply glucose. On the other hand, by focusing the diet on non-starchy (low-carbohydrate) vegetables, protein and fat, and basing carbohydrate consumption on activity levels, fat is free to leave the cell and can be burned to supply energy needs.
In this case, if someone chose to reduce total calorie intake while also keeping insulin levels low through nutrition choices, weight loss could occur at an increased rate. The issue is, too many people focus first on calorie reduction rather than the quality of the foods they eat. Simply lowering calories while still eating a significant amount of carbohydrates is a recipe for lowering metabolic rate, losing lean body mass, constant hunger and eventual failure on the plan.
Changing your perspective on food choices
That is not the case, so you must think for a moment before you put something in your cart. The easiest question to ask is, “If I eat this, how will it affect my body’s hormones?” It isn’t about eating a few extra calories of food, it’s about whether or not you trigger the release of insulin or add extra stress to your liver. If you avoid stressing your liver and stimulating insulin, there’s a good chance you’ll also avoid weight gain or achieve the weight loss you’ve been looking for.
A final thought on this topic is that even though the food you select will have the most significant role in whether you achieve the weight loss you’re looking for, it is not the only issue. When we help people with their weight management programs, nutrition is a big part of the discussion, but we also look at movement, metabolic health, exercise, stress and sleep, and your mindset. Each of these plays a role as well. That said, we also encourage people to tackle one thing at a time, and if you want to get the most “bang for your buck,” stop counting calories and start focusing on eating quality food.
This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.
[i] Zoë Harcombe. The Obesity Epidemic: What caused it? How can we stop it? Columbus Digital Services Ltd. 2010