Everyone who has ever even considered going on a diet or losing weight has heard of the idiom “3,500 calories equals 1 pound of weight loss”. So, what does that actually mean? Before we get into that, it is important to master the concept of the often times dreaded “calorie”.
A calorie is simply a measure of a unit of energy. In its most scientific definition, a calorie is the amount of energy that is required to raise the temperature of 1 gram of water by 1 degree Celsius. Because energy is only transferred – it cannot be created or destroyed – scientists use what’s called a bomb calorimeter, like the one below. They essentially burn the food inside of the bomb cell and note how the temperature of the surrounding water changes. Pretty fancy way of counting calories – thank goodness for food labels!
However, the calories that you see noted on a food label are in bigger units – times 1,000, in fact. They are denoted with a capital “C” – Calorie, or in the research world known as a kilocalorie (kcal). However, for ease of this article, calorie and Calorie will be used interchangeably.
So, where do we get calories? These little tasty bundles of energy come from our macronutrients, which include carbohydrates, fats and proteins. So everything else – for example vitamins and minerals – do not contain any energy and therefore do not contribute to our caloric intake. This energy that we consume is either burned to fuel us with energy, or the excess it stored. It can’t just dissipate into thin air! So those French fries that you just had at lunch are either going toward your workout or your thighs!
Back to what we started talking about. The phrase “3,500 calories equals 1 pound of weight loss” then
means that in order to lose 1 pound of weight, one must create a caloric deficit of 3,500 calories. It is
important to mention that in this conversation, we are talking about TOTAL weight loss including both fat, and sometimes even muscle (sorry, meatheads – I know that’s painful) – so the number on the scale.
We will talk about how to try to maintain muscle mass during a caloric deficit in a later conversation.
Now, for simplicity sake, let’s say you wanted to lose 1 pound of body weight per week (1-2 pounds per week is recommended to optimally maintain the weight loss). With this logic, you would need to cut out 500 calories per day from your total calorie intake (3,500 calorie deficit / 7 days per week = 500 calories per day). If you are eating a standard 2,000 calorie diet, that means in order to lose 1 pound per week,
you would have to shift to only consuming 1,500 calories per day, consistently. Even further, if you
wanted to lose 2 pounds of body weight per week, these numbers would double!
But, what does the science say? In a study by Thomas et al., (2013), researchers conducted a meta-analysis of seven weight loss experimental trials to determine whether or not the 3,500 calorie rule to predict weight loss was a feasible estimate of actual weight lost (1) . Despite the ubiquitous use of this rule by everyone from personal trainers to governmental dissipated information, these researchers concluded that the 3,500 calorie rule and the consequent predicted weight loss is actually a gross OVERESTIMATE of actual weight loss.
Each of the points in the graph above represents an individual participant in one of the seven analyzed
studies. Most of the points, as you can see, fall above the average line – I would venture to say about 75- 80% of the points. Let’s take a further look at what a point that resides above that line means.
Let’s consider the point that I’ve circled above. The red dotted line indicates the predicted weight loss of that individual in their respective study using the 3,500 calorie rule. As an estimate, let’s say that it lines up with ~25 pounds of predicted weight loss. The blue dotted line indicates the actual weight lost of that individual in their respective study using the 3,500 calorie rule. This one looks like it lines up with ~19 pounds of actual weight loss. For this individual, that’s an overestimate of ~6 pounds of weight loss.
Now, this may not seem like too much of a difference to some of you – but to others, that’s the difference between having to get your wedding dress altered or not!
What can we take away from this article? Well – in these 7 studies, the main mechanism (and most of the time the only mechanism) that they used to make these participants lose weight was a decrease in caloric intake. In research, it is important to try to control almost every variable – and the only way that researchers can do that if they are only trying to look at lowering calories – is to keep everything else constant. This includes exercise!
So, it seems as though if you are looking to lose weight simply by reducing calories, and not necessarily by changing your workout routine, you may have to use a greater caloric deficit. However, there are some issues here. Reducing calories by more than 500 calories per day – let’s say 600 per day which would give you a 4,200 calorie weekly deficit - can lead to negative metabolic implications that are often associated with starvation. This may include pulling a greater part of body weight from your muscle and bone – and we know that greater muscle mass keeps our metabolism high! So of COURSE we don’t want that! Your resting metabolic rate (the calories that you burn simply sitting there) may also decrease because your body is trying to preserve itself. Your body literally thinks that you are trying to kill it because you are restricting it of the calories that it needs to survive! So metabolism will slow in order to preserve the limited energy sources that it has floating around.
There are a couple of other options, though. One being to increase the amount of protein that you are
eating. Protein is known to increase metabolism and contribute to an increase in muscle protein building, and at some levels in some populations begins to slow down muscle protein breakdown.
Protein is also known to be lipolytic – meaning that is helps transport stored fat from your fat cells into the blood and then potentially into muscle tissue to be used as energy (what you know as fat BURN). Protein is also antilipogenic meaning that it blocks the GROWTH of fat cells. DOUBLE BONUS!
Lastly, of course, you can add an exercise regimen or increase the intensity of the one you are currently performing. Exercise for weight loss is a whole other ball game that we will get into later, but there are some great workout methods to employ that are SURE to work to fire up your metabolism: resistance exercise training and high intensity interval training. Let’s save those conversations for later!
TAKE-HOME MESSAGE: if you are looking to lose weight just by restricting calories, a 3,500 calorie weekly deficit may not be enough – you should consider adding protein to your diet or changing up your workout routine!