Energy balance is the term used to describe the relationship between energy intake and energy expenditure. i.e. Calories in vs Calories out.
The energy balance principle is THE GREATEST PRIORITY for any fat loss attempt. It is the underlying principle that results in changes in body fat.
The balance between energy intake (calorie intake) and energy expenditure (calorie expenditure) over time will determine whether you maintain, lose or gain fat/weight.
- If you are in a negative energy balance, also called a calorie deficit, where calories in is less than calories out, you will lose fat.
- If you are in a state of energy balance, also called maintenance calories, you will maintain your current level of body fat.
- If you are in a positive energy balance, also called a calorie surplus, where calories in is more than calories out, you will gain fat.
While it may come across that weight management is as simple as calories in vs calories out, things aren’t quite so simple. As you can see, there are multiple components to both calorie intake and calorie expenditure and they can all have an influence on your resultant energy balance.
Something that is essential to understand is that energy balance is DYNAMIC!
This means that energy balance will constantly change in response to a number of (biological and behavioural) factors. A change in something on one side of the equation (e.g. energy intake) can influence factors on the other side of the equation (e.g. energy expenditure) in unpredictable and sometimes unintended ways.
For instance, if you are in a calorie deficit and lose weight, your basal metabolic rate and total energy expenditure will reduce as less energy is needed to fuel and move your smaller body. As you lose weight your body requires less calories to meet its energy needs and maintain its current weight.
Another example may be that if you are in a calorie deficit and losing weight, you might consciously and/or subconsciously reduce your NEAT (energy expended from activity that is not intentional exercise) by choosing not to move as much, not taking the stairs or fidgeting less etc. Your body wants to maintain its current state (homeostasis) and can employ strategies that result in reduced energy expenditure e.g. making you feel tired so you don’t want to move. This reduction of total energy expenditure will reduce the size of your calorie deficit. It’s possible that your NEAT and total energy expenditure could reduce enough that you are no longer in a calorie deficit.
This paragraph above could explain why your fat loss has plateaued!
The dynamic interplay between the two sides of the energy balance equation should not be overlooked.⠀⠀⠀
As Uncle Martin Macdonald says “weight loss is as simple as calories in vs calories out, it’s just that calories in vs calories out isn’t that simple”.
Let’s take a deeper look at the 3 states of energy balance
Maintenance Calories (Energy Balanced)
Achieved when calorie intake is equal to calorie expenditure. If calorie intake and expenditure are equal over a period of time weight will be maintained.
Maintenance calories will change depending on your energy balance history. ⠀⠀⠀⠀⠀⠀⠀⠀⠀
For instance, if you have been in a negative energy balance for a period of time and lost weight, your maintenance calories will be less than what they were before you started losing weight. You’re now a smaller human so you require less calories to fuel your body. This is part of the reason why you need to have a plan for when the fat loss phase of your diet has finished.
Because, if you go back to your previous level of calorie intake (prior to weight loss) and neglect the change in calorie maintenance, you will end up in a calorie surplus and likely regain the fat you lost.
You should return to your new maintenance calories as soon as possible after a dieting phase
The Calorie Deficit (Negative Energy Balance)
Achieved when Calorie intake is less than Calorie expenditure and results in fat loss.
Important for those wanting to lose fat. If you’re not in a calorie deficit, you won’t lose fat.
If you needed 2400 calories per day to function and support your activity levels but you consume only 2000kcal, your body needs to dig into its stored energy for the extra 400kcal to fuel your body. If overtime your calorie intake is less than what your body requires, you will use more and more of the stored energy which will result in fat loss.
Any means of creating a calorie deficit will result in fat loss. A calorie deficit may also result in the loss of muscle mass.
A way to ensure weight lost is fat and not muscle is to have adequate protein intake and perform resistance training that provides enough stimulus to maintain muscle tissue.
If you tried one of the many diet methods out there and didn’t lose weight, it’s because you were NOT in a state of negative energy balance, a calorie deficit was NOT present.
If calories in is less than calories out, you are in a calorie deficit and you will lose fat.
Remember, energy balance is dynamic. If body fat is lost from reducing calorie intake, basal metabolic rate (BMR) can decline because a smaller body requires less energy. This can cause total daily energy expenditure (TDEE) to fall below predicted levels.
If exercise and moderate caloric restriction are combined to achieve weight loss, TDEE is maintained at or above estimated levels. So maintaining higher daily energy needs (via increasing energy expenditure) can make It easier to maintain body weight after a dieting period.
For example, 70kg female loses 10kg, her BMR & TDEE will now be lower and depending on calorie intake she may achieve energy balance (i.e. no more fat loss). But, if she were to expend energy via continuing to exercise or keep NEAT high, this may increase TDEE so that a negative energy balance is maintained for longer resulting in further fat loss.
Because BMR will now be lower than it was prior to weight loss, she may need to continue expending more energy when she returns to caloric maintenance so as not to end up in a calorie surplus and gain weight. This is why having an exit strategy and exercise are helpful for maintaining weight after a fat loss phase.
The Calorie Surplus (Positive Energy Balance)
Achieved when Calorie intake is larger than calorie expenditure and when results in fat gain.
Important for those who don’t want to gain fat and those that are trying to gain weight.
Any means of creating a calorie surplus will result in weight gain and fat gain. Whether weight gained is mostly fat or muscle will be influenced by the size of the surplus and other factors such as exercise or macronutrient composition of the diet.
The larger the surplus, the more fat you will gain.
When you consume more energy than your body needs it stores energy for use later. This energy is stored as fat or glycogen. Fats are stored as triglycerides in adipose tissue which is made up of adipocytes (fat cells).
Adipose tissue can store large amounts of energy as fat. A non-overweight person weighing 70kg and only 10% body fat would have 7kg or 7,000g of body fat. There are 9 calories for each gram of fat so 7,000g x 9cal = 63,000 calories of energy stored as fat.
If energy intake is larger than energy expenditure and body weight increases, BMR and total daily energy expenditure will also increase due to the greater energy requirement of maintaining and moving a larger body.
The body will put in place some strategies to reduce fat gain. For example, you may unknowingly increase your activity level in an attempt to expend more energy so as not to gain more weight. Eventually, energy balance may be achieved at a higher body weight.
Understanding energy balance, its dynamic nature and its components is crucial if you want to manage and take control of your weight.
Dynamic Energy Balance: An Integrated Framework for Discussing Diet and Physical Activity in Obesity Prevention—Is it More than Eating Less and Exercising More? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5579698/