By Lindsay Wilson
Want to know how to lose body fat? Focus on your deficit!
There’s a popular story in business circles that goes a little like this:
When Bill Gates first met Warren Buffett it was at a dinner party hosted by Gates’ parents. After chatting amongst themselves for hours Bill and Warren rejoined the masses, at which point everyone around the table was asked to identify what they believed was the single most important factor in their success. Gates and Buffett gave the same succinct answer: “Focus”
It’s a wonderful answer of course. The world is full of stories about people that find something they love to do and then focus relentlessly on getting better at it. But it begs the question, where should I focus?
When you set out to lose fat having a focus is hugely helpful. Some people focus on exercise, others count calories, many cut carbs and some limit processed foods. But when you research the methods in natural bodybuilding, the sport all about losing fat while maintaining muscle, you’ll notice one very clear trend amongst the best.
They all focus on the caloric deficit!
In this first section of The Fat Loss Framework we are going to talk about energy. We’ll look at where our energy comes from, the way we expend it and how the balance between these two affects weight loss. We’ll also learn why these components are mutually dependent then finish with a summary of what this means for someone losing fat.
The basics of a caloric deficit
When it comes to fat loss the deficit we are interested isn’t the government’s budget, it’s the ‘caloric deficit’. This is when we expend more energy than we absorb from food over a set period (typically a day).
The reason body-builders focus on the caloric deficit is that creating one it forces the body meet the energy shortfall from its energy stores. These energy stores are glycogen (stored carbs), muscle tissue (stored protein) and body fat (stored fat). With glycogen in relatively limited supply the aim is to maximise the energy dragged from fat cells by maintaining as much muscle mass as possible.
The whole concept is a lot easier to explain visually:
In this graph the caloric deficit is the section in the middle. This is the amount of energy the body has to draw from its energy stores to maintain energy balance. On the left hand side is the energy absorbed from all the food and drink that is eaten in the day, and on the right hand side is the energy expended.
Energy expenditure is the sum of energy used by the body in the day. For almost everyone but athletes and physical labourers resting metabolism takes up over half of expenditure, digestion of food is around a tenth of total calories. Activity from general and subconscious movement like fidgeting can vary greatly between people, and exercise is typically a smaller fraction with the exception of athletic individuals.
Although the deficit is the state we want to achieve for fat loss it is still important for us to get our head around how we gain and maintain weight, as these will both be things we will want to do at other times.
Bottom line: In a deficit the body draws energy from its stores
Types of daily energy balance
The state of positive energy balance, where we eat more than we expend, is called a caloric surplus. This is how we gain weight and is a common occurrence in the holiday periods and often at weekends too. A small caloric surplus is a good state to be in when you are trying to gain some muscle and it increases the time spent in an anabolic state.
When energy consumption matches expenditure, and things are roughly balanced out, this is what we call maintenance. Although energy stores are never truly static, if you are maintaining a stable weight then your average daily calorie consumption will be close to maintenance. Working out what this is before you start a diet is a very good idea!
Once again I find it much easier to explain graphically.
On the left hand side we have the caloric surplus, the state in which weight is gained. In the middle is maintenance, where we maintain weight. And to the right is the deficit, the state we use to lose weight.
For the purpose of explaining things easily people often only refer to energy balance by looking at one day, as we have done here. But in reality it’s much more dynamic.
Our body goes in and out of periods of storing and liberating energy throughout the day. We are typically in positive energy balance following meals and then drop into negative balance after a few hours after eating, particularly so during sleep.
We generally use the concept of daily energy balance because it’s so useful, but we can also stretch the time period out however we want. You can easily consider a week, a month or even year.
Personally I find focusing on whether you are in a deficit across a week really useful, as it open ups lots of avenues for cyclical approaches that can break up the monotony of a diet. Likewise, over the course of a month the scale is a very good indicator of what your energy balance has been like, as this tends to be long enough to smooth out all the fluctuations in water retention that can mask what is happening with your muscle and fat mass.
In general having a flexible approach to the idea of energy balance is useful, because your body has a sneaky habit of moving the goalposts.
Bottom line: Energy balance can be in surplus, deficit or maintenance
Simplistic fat loss
Although understanding energy balance can be an incredibly useful starting point for losing weight, the most popular way it is described is far too simplistic.
It’s often called the ‘3,500 calorie rule’ and a common version goes like this:
cut 500 calories a day and you’ll lose a pound of fat a week
Here’s what it might look like in terms of our visuals:
Now if you happen to be a woman that expends about 2,000 calories a day, or a man that burns 2,500, this type of deficit will be a great start for you. But to assume its going to result in losing a pound a week for as long as you keep it going is just plain wrong. And thinking this way is a huge source of frustration for well meaning people.
Think about it for a minute. Lets say the woman in the graph that expends 2,000 calories a day weighs 160 lbs (73 kg). Does anyone really think that if she ate 1,500 calories a day for 3 years she would simply disappear? Of course not, we know intuitively that is wrong. Our body will adapt to what we feed it.
So how did we get in this mess of terrible thinking? In the 1950s Max Wishnofsky wrote a paper that seems to have birthed this monstrous meme.
Here’s the math. A pound human body fat (454g) is about 87% adipose tissue (fat) and the rest mainly water. That’s 395 grams of fat which contains about 9 kcal/g. This multiplies out to 3,555 calories of available energy in a pound of fat. Which rounds beautifully to 3,500, which neatly simplifies to 500 calories a day for a week.
The paper did dieters the world over a serious disservice by comparing this type of calculation with some clinical studies of low calorie diet results and concluding that:
The low-calorie diets on which individuals are placed for the purpose of weight reduction should be high in protein so that protein and glycogen will be approximately in equilibrium. The calorie deficit will be made up chiefly by the catabolism of fat. Under the circumstances (high-protein intake) the caloric equivalent of one pound of body weight lost is approximately 3,500 cal.
And so the meme was born, seductive in its elegant simplicity.
The first problem with the ‘3,500 calorie rule’ is that we don’t lose just fat in a deficit. We know from more modern metabolic ward studies that people in deficits also lose muscle tissue and ‘water weight’ from glycogen. Due to its high water content muscle yields about 700 calories per pound while glycogen gives just 500 calories per pound. This helps explain why very low calorie diets can yield rapid weight loss (muscle is metabolised) and how low carb dieters often drop a few pounds in their first week (‘water weight’ is lost from glycogen).
The second problem is much worse. People assume this ‘rule’ can be extrapolated to ‘losing a pound of fat a week’ over long periods. As we’ll see in a minute this idea sets up unrealistic expectations. Even the original author observed that ‘as weight loss occurs caloric expenditure decreases’. He knew back in the fifties that energy balance was dynamic, but somehow the seductive elegance of ‘500 calories a day’ just never seems to disappear.
Bottom line: Energy balance is dynamic and changes over time
How we adapt to overfeeding
To avoid giving you the impression that energy expenditure only adapts in a downward direction, lets first look at what happens when people are overfed.
The following graph comes from a really famous study that coined the phrase ‘nonexercise activity thermogenesis’ (NEAT). In these graphs I simply call it ‘activity’. It’s the energy expenditure made up of things like fidgeting, maintenance of posture, shivering and other physical activities in daily life. Basically everything that isn’t resting, digesting or formal exercise.
In the study James Levine and colleague took 16 healthy individuals and overfed them each by 1,000 calories a day for 8 weeks. Here is a rough graphically summary of what happened to their energy balance over the eight week period, averaged across the group.
The average weight gain across the 8 participants was about 10 lbs (4.7kg), less than half of what a static energy balance calculation might predict.
What they found was that by the end of the eight weeks average energy expenditure had increased by 554 calories a day, reducing the surplus by over 50%. People’s bodies used more energy in response to overfeeding.
Perhaps even more fascinating was how the weight gain and expenditure varied amongst the group. The weight gain ranged from 3lbs (1.4 kg) up to 15 lbs (7.2 kgs). The thing that caused most of the variation was how activity changed (their NEAT response). This went all the way from a 98 calorie drop to a massive 692 calorie increase. The conclusion was that some people have a strong activity response to overeating, helping them stay naturally slim, while others are weak responders predisposing them to a higher obesity risk.
Of course this is just one study, but it does give us a good basic look at what happens when we overeat. Our metabolism up-regulates itself and we eventually settle at a new heavier weight, once energy expenditure has caught up with the overeating. Of course the amount of weight gain could vary greatly depending on how ‘responsive’ we are.
It’s also important to remember overeating can have a time and place. The benefit of eating more to upregulate your metabolism is reflected in nutrition protocols like re-feeds, diet breaks, cyclical diets and fasting protocols (the non fasting days).
Bottom line: We adapt to overfeeding by gaining weight and increasing expenditure
How we adapt to dieting
Just as our body adapts to overeating, it will also adapt to going on a diet.
Tragically, for those of us looking to lose weight there is some evidence that our bodies are much better at defending us from fat loss than they are at protecting us from fat gain. This makes sense from an evolutionary perspective as getting very lean leads to reproductive problems, whereas having extra fat might have been quite useful during periods of food scarcity.
To provide another visual example I grabbed some data from a great free living study that looked how people adapt to caloric restriction. I’ve used data from 12 people that were placed on a 25% caloric deficit for three months. Here’s what their average adaptation looked like:
Over the three months on a 25% calorie restriction the 12 healthy individuals in the group lost an average of 13 lbs (6kg). After three months on the diet the original 712 calorie deficit had been reduced to just 258 calories.
Average energy expenditure fell by 454 calories, mostly drops in activity and to a lesser degree resting metabolism. The adaptation was 371 calories greater than what was expected from the change in muscle and fat mass alone. This additional loss in expenditure is what people in the field call ‘adaptive thermogenesis‘.
Basically the whole process of losing weight results in the body getting more efficient in maintaining cells, organs and tissues, as well as reducing our subconscious activity in order to conserve energy. This makes regaining weight particularly easy to do after significant weight loss, and may explain part of the reason a majority of people who have lost a lot of weight and kept it off do a lot of exercise each day.
Again this is just a single study but the existence of these adaptations to dieting is pretty well established now. There is even a study that shows the huge drops in resting metabolism that occur during The Biggest Loser competition. Complete with the depressing conclusion that this can predispose people to weight regain ‘unless high levels of caloric restriction or physical activity are maintained’.
While its easy to take a rather defeatist approach to this information it can also be super useful. Not only does knowing some level of adaptation is inevitable make you more patient, but it serves as a reminder that maintaining a healthy metabolism should be a priority for everyone losing weight.
Bottom line: We adapt to dieting by losing weight and decreasing expenditure
Moving beyond the ‘3,500 calorie rule’
By this point I hope you’ve got the idea our energy expenditure is intrinsically linked to what we eat, and that the balance between consumption and expenditure is a dynamic one. I also hope that you understand why this means the 3,500 calorie rule is pretty useless once you are talking about months instead of weeks.
But for those of you that still aren’t quite ready to let go of this idea have I’ve got a fun little chart. It’s based on one of the only dynamic models of human energy balance that have actually been validated against data from controlled trials.
This graph models the bodyweight of a 220lbs (100kg) man that permanently cuts his food intake by 500 calories a day, from 3,000 down to 2,500. The orange line is the expected results from the dynamic model of energy balance, while the black line tracks what would happen if the ‘3,500 calorie rule’ did hold true indefinitely.
After a year on 2,500 calories a day the ‘3,500 calorie rule’ implies estimates weight loss of 49lbs (22kg), in the dynamic model it’s just half of that. Stretch the ‘3,500 calorie rule’ out to four and half years and our man simply disappears 😉 Whereas in the dynamic model his bodyweight plateaus at a new bodyweight of roughly 165lbs (75kg), a much more logical figure for a man eat that much.
The ‘3,500 calorie rule’ makes no sense over long periods. I personally don’t think it needs a replacement but if you are desperate you could do worse than this one suggested by a panel of experts:
every permanent 10-kcal change in energy intake/d will lead to an eventual weight change of 1 lb when the body weight reaches a new steady state ( ∼ 100 kJ/d per kg of weight change). It will take nearly 1 y to achieve 50% and ∼ 3 y to achieve 95% of this weight loss.
If you want a rough idea of what that might look like, in a theoretical word of perfect diet compliance, then check out the NIKK’s Body Weight Planner. And remember that your body isn’t stupid, it is going to react to what you put in your mouth. Our species didn’t survive the ice age without the ability to get thrifty with energy when it ran short of food. So if you want to peel off slabs of fat over a long period you’d better be prepared for some moving goalposts.
Bottom line: Our metabolism is adaptive and changes due to stimulus
Hormones, homeostasis and health
At this point it’s pretty clear that energy balance is dynamic. In particular we know that expenditure will probably go up when we overeat and down when we diet. But this doesn’t really explain why. And although the fact that a lighter body uses less energy is pretty intuitive, there is clearly a lot more going on.
The discovery of Leptin in 1994 was probably a turning point in our understanding how profound the effect of hormones are in regulating our bodyweight. With hindsight the existence of some type of regulatory system makes perfect sense, as a grown adult might consumes a million calories a year but generally ends up within a few pounds of their starting weight.
Leptin is a hormone made by fat cells that acts on receptors in the hypothalamus, a part of the brain. When our levels of body fat drop so too do our Leptin concentrations. This is sensed in the brain which stimulates appetite and suppresses energy expenditure in an attempt to restore fat mass and bring the body back towards ‘homeostasis‘.
And Leptin is just the beginning. There are numerous hormones involved in regulating energy balance. Ghrelin is a hormone from the pancreas that regulates hunger, insulin modulates how we switch between fuel sources, then there the sex hormones, growth hormone and a growing list produced in the gastrointestinal tract. Over the last ten years there has been an explosion of research in this area that will hopefully give us more tools to deal with obesity in the future.
For the purposes of this framework we simply want to recognize that this hormonal regulation system exists. We won’t try to target specific hormones, as for individuals this is fraught with complexity, but instead acknowledge that to lose fat and keep it off we also need to defeat a physiological drive to restore fat mass. This can reminds us to be kind to ourselves when things don’t go to well and vigilant when they do.
Using this knowledge we can improve our idea of energy balance to look like this:
This graph is a very simplistic attempt to modify our energy balance graph to include these hormonal feedback loops. I’ve only included some key hormones like leptin, insulin and ghrelin on this, but rest assured the complexity of the system as a whole is mind blowing.
The existence of a hormonal regulation system begs the question of whether we should be looking to influence our hormones to modify energy balance, rather that the other way around. I think this is a wonderful question, but personally feel that as an individual trying to change my own weight it is much easier to frame the problem in terms of energy balance first. Although I might consider my food choices, macro ratios or exercise selection with an eye on my hormonal health, I still do this within the framework of getting my overall energy balance right.
The effectiveness of creating a deficit by controlling what you eat is so well evidenced in metabolic ward studies that for most healthy individuals the real challenge isn’t a scientific one but instead a behavioural one of diet adherence. Add in some basic elements like resistance training, sufficient protein and adequate fat, and hormones have a tidy habit of falling into line when you get the deficit right.
Bottom line: A complex web of hormones defends fat mass
How to lose body fat?
At the start of this section I told a little story about the importance of focus. And focus is the reason why energy is at the centre of the Fat Loss Framework. If I could only give four words of advice to someone trying to lose fat it would be this:
Focus on the deficit
Why? Because the deficit is the energy shortfall you need to lose fat.
Even if you do all the ‘right things’ like lift heavy, eat adequate protein, choose mostly whole foods and add strategic cardio, your body is going to be decidedly unimpressed by your efforts unless your average daily caloric intake comes in below your energy expenditure. It is quite simply the one thing you need to get right before proceeding to anything else.
Here is my attempt to explain what ‘focus on the deficit’ means visually.
The image above is a stylized version of what a six month fat loss program could look like for a man going from 180 lbs (82 kg) down to around 160 lbs (73 kg). Our area of focus is the caloric deficit, the section coloured with grey stripes above the energy consumption but below energy expenditure.
The dynamic nature of energy balance means that energy expenditure (the orange line) is affected by energy consumption (the black line). So the adjustments we make to diet and exercise will change depending on where we are at in the diet cycle. This is easiest to understand in a time sequence.
- 1) To begin with calories are reduced by 500 from maintenance (2,800) down to 2,300 kcal/day. Full body strength training begins twice a week and the share of protein in the diet is raised to help maintain muscle mass and stay full.
- 2) After some rapid weight loss in the first two weeks (partly water) things have slowed down to a pound a week by week six. While maintaining the 2,300 kcal/day, lifting and adequate protein, the trainee adds in 30 minutes of steady state cardio a day. This boosts net expenditure by roughly 200 kcal/day.
- 3) Having lost an impressive 11 lbs (5 kg) to date weight loss has slowed again by week 12. Hunger is starting to become a problem, and the trainee is feeling tired. A two week diet break is taken, returning to 2,800 calories a day and ceasing cardio. This is a break from both a the physical and mental stresses of dieting.
- 4): Although he’s gained a few pounds the dieter is feeling good again. This time calories are cut further to 2,100 kcal/day, most of which comes from carbs. Strength training and sufficient protein are again in place, cardio is held back for the moment.
- 5) Still progressing and feeling good the trainee decides to add cardio again to move things along. This is again 200 kcal/day, 30 mins of cycling while watching TV.
- 6) 20 lbs (9 kg) lighter and happy with his new body the trainee is now looking to maintain. He ads back calories each week until he finds his new maintenance, around 2,600 kcal/day. As a lighter and leaner individual this is lower than before, but with increased training he should be able to edge this up over time without fat gain.
Now just to be very clear, this graph is simply a stylized example. Individual energy needs vary greatly and nobodies intake or expenditure will ever look this smooth in real life.
The specific calories, weight loss and time period given here are not what’s important. The point is this. You need to find a way to get yourself into a caloric deficit and keep yourself there for long enough to see some meaningful fat loss. And you need to do it with a body that want’s to keep its fat in a food environment that facilitates overeating.
This is what it means to ‘focus on the deficit’. Your body, you environment and your lifestyle make fat loss hard. So you need to know where to focus your efforts.
Bottom line: The deficit is the first priority of fat loss
Focusing on the deficit makes weight loss easier. Maintaining a caloric deficit is harder than it first seem because your body will defend its fat by making you hungry and more frugal with energy. This is why we often need to adjust our approach to continue progressing.
In the next step we’ll look at what the best foods for weight loss are.