How to lose body fat and get lean – Complete guideWeight loss 101 | Science broken down
It always seems strange to me that weight loss is still one of the most debated and discussed topics amongst people both in and out of the fitness “world”.
People come up with different diets, equipment and workout programmes every single day it seems, capitalising on people’s lack of knowledge – it’s a massive shame.
There is, for all intents and purposes, only one single way to lose body fat: A calorie deficit. The end.
Okay maybe not the end, but still kind of the end.
In a rush/not interested in any mumbo jumbo?
Scroll down to the summary at the bottom for an overview of the necessary process for effective fat loss.
Weight loss all comes down to your “energy balance”.
Intuitively, this makes a lot of sense, or at least it should do anyway.
Every single day, we consume energy (calories) through our food/drink choices, and we also expend energy (calories) via simply being alive, walking, exercising, talking etc.
So there’s a constant push/pull relationship whereby on one hand, you’re taking in energy and on the other, you’re expending it – this is referred to as your energy balance, and it’s a crucial element to achieving any of your fitness goals.
In order for weight loss, we require that over a given period (let’s say 24 hours), we are in a state of negative energy balance: A calorie deficit where our energy intake over 24 hours has been lower than our energy output. Makes sense right?
‣Energy Balance: Calories in vs Calories out.
‣Calorie Deficit = Calories in < Calories out. This is referred to as a negative energy balance and is required for fat loss. Over a given time period, weight loss occurs when the calories consumed are less than the calories expended.
Before I continue any further, I’d like to address something. This is not meant to be an academic article in biological science; there are always much more intricate details regarding physiological processes such as this. The take home point however, is that these details bear virtually no practical relevance in the real world and treating weight gain/loss as a simple case of calories in vs calories out will serve you perfectly well for the rest of your time on this planet.
Let’s talk numbers – your TDEE (don’t worry, it’s simple).
So, to lose weight, a calorie deficit is required (assuming you’re wanting to lose fat that is, otherwise you could cut your arm off and lose weight whilst eating all the calories you want).
How do we go about quantifying and facilitating a calorie deficit?
Firstly, you need to calculate your TDEE (Total daily energy expenditure) – this will inform you the amount of calories you typical expend on a daily basis, and therefore is the amount of calories you need to consume in order to maintain your current bodyweight. How do you calculate your TDEE you ask?
‣BMR: Basal Metabolic Rate. The amount of calories your body burns at complete rest. It is composed of your height, weight, lean body mass, gender etc. Our bodies require/burn a certain level of calories each day even if we are completely inactive.
‣TDEE: Total Daily Energy Expenditure. This is the amount of calories you actually burn each day, and is the sum of your BMR + Your activity level*. This number of calories is the amount of calories required per day for you to maintain your weight.
*Activity level includes everything you do, from lifting weights to typing on a keyboard. More accurately, it is the sum of your TEF (thermic effect of food), TEA (thermic effect of activity) and NEAT (non-exercise activity thermogensis). – Don’t worry about this too much.
Check out my free calculator to determine your TDEE (maintenance calories) right now here:
What this will give you is an estimation of your TDEE, and from here, you can work out with a pretty good degree of accuracy the amount of calories required daily for you to achieve your desired rate of weight loss. I’ll break the process down:
- Work out your estimated TDEE by using the calculator.
- Begin tracking your food every day for 14 days straight, and weigh yourself every day first thing in the morning (to determine an average).
- If your weight does not alter between the two weekly averages, you can happily accept that this is, for all intents and purposes: your TDEE.
- If you gain weight, this estimation is slightly too high, and your maintenance calories will actually be slightly below that estimation. If you lose weight, the opposite holds true.
- From here, you can get a pretty good idea of your maintenance level of calories, and can now begin your weight loss journey.
The fat loss begins – your very own calorie deficit.
Okay, you’ve now worked out your TDEE, and you know you need to consume less calories than your TDEE (hopefully you’re still with me). So how many calories do you consume?
You want your weight loss to not be too aggressive, but also not at a snail’s pace because both come with far too many downsides.
Generally, I would recommend one reduce their calories by between 15 and 25% from their TDEE, depending on how much weight they have to lose. If you have more weight to lose, I’d opt for the 25%, and gradually decrease the deficit as the individual’s body fat percentage decreases.
This is simply because dieting becomes harder and harder the leaner you get, and adherence is crucial in any well-structured diet (you never want to be forced in to eating fewer calories than what is necessary, it is entirely counterproductive).
A practical example
‣An individual whose maintenance calories are 2400, and is not currently medically overweight with not too much body fat to lose, would reduce this number by 15% (360) to determine their daily weight loss calories: 2040.
‣A heavier individual with more body fat to lose, whose maintenance is say, 2800 calories, may reduce this number by 25% (700) to determine their weight loss calories: 2100.
Both of these are hypotheticals and you should determine your own desired rate of weight loss based upon a diet you can comfortably adhere to without unnecessary additional psychological and physiological stress.
Think of it this way: Weight loss requires a calorie deficit – it is necessary. However, at all times during a diet, you want to be consuming the maximum amount of calories possible whilst still losing body fat.
Don’t start thinking that faster weight loss = the best possible outcome for body fat reduction. It’s a marathon, not a sprint (I hated typing that cliché as much as you hated reading it).
Determining the best approach for you as an individual.
I would always recommend your weight loss be slower rather than faster, as there is plenty of literature supporting this – One study showed that a reduction in bodyweight of 0.7% per week had clear advantages over losses of 1.4% per week in multiple aspects.
That is not to say however, that you should make your diet last as long as possible – it’s about achieving the maximum rate of fat loss before negative side effects occur (the law of diminishing returns), which just so happens to be a reasonably slow rate.
However there’s still individual variation to factor in here. As already stated, and will be stated over and over, the best “diet” is the one you can comfortably adhere to.
I mean, all weight loss boils down to is your degree of calorie deficit, so you may as well try and enjoy the calories you can consume so that the psychological stress of dieting can be alleviated to some extent.
This means that the foods you eat, the times that you eat them, the rate of weight loss you opt for – they should be based around you as an individual. I’d recommend nearly everyone falls in to the 15-25% calorie deficit range as previously mentioned, but know that there are no hard and fast rules as to where in that range you should fall – you need to figure out for yourself what works for your body, and allows a steady, consistent (but not linear*) reduction in bodyweight.
Some people will feel more comfortable dieting faster than others, depending on a huge variety of factors. Find what works best for you, just keep it reasonable.
*Weight loss is not linear – you can be eating an amount of calories that should consistently produce 0.5lbs loss per week, and some weeks you will lose more and some less: focus on the average and monitor the longer trend, not the day to day variation.
Potentially useful information
1 lb of fat is equivalent to roughly ~3500 calories, and therefore the often intuition is that eating at a 500 calorie deficit per day will yield 1lb lost per week (as 500calories * 7days = 3500calories).
I feel like I must stress the importance of appreciating that this is a rule of thumb, not a law in reality.
Theoretically, this is reasonably sound – but the body does not lose purely adipose (fat) tissue when placed under caloric restriction, there are losses in glycogen, water & LBM (lean body mass).
As well, there are metabolic adaptations to factor in that accrue over a prolonged period of dieting.
Basically, if you calculate what you believe to be a 500 calorie deficit per day, don’t expect to see an exact loss of 1lb every 7 days – our bodies are not that simple (it’s still perfectly plausible that you may be losing 1lb of actual adipose tissue each week however, but it may be “behind the scenes”) .
Meal timing & food choices – cue flexible dieting, or, “IIFYM”.
Your diet should work around your lifestyle and not vice versa. As we know that weight loss comes down to our energy balance – we can now deduce that the choice of food, and/or the times at which they are consumed, are of much lesser importance than may have once been hypothesised. This is where the notion of flexible dieting comes in to play.
Your macronutrients (macros):
Calories come from macronutrients: Protein, carbohydrates, and fats (and also fibre and alcohol).
It is important to eat a somewhat sensible balance of all 3 macronutrients as opposed to just blindly focusing on calories. For example: If you were to simply focus on calories, then a diet of purely cookies would be sufficient providing you are in a calorie deficit.
Yes, you will lose weight (calorie deficit), but this is not a sensible diet by any stretch of the imagination – devoid of micronutrients, lack of fibre, insufficient protein, low satiety, difficult to adhere to over time etc.
Although calories are king, macronutrients are a close second in terms of importance as they help ensure your diet is actually successful in eliciting the results you desire.
Protein (kcals per gram)
Carbohydrates (kcals per gram)
Fats (kcals per gram)
Fibre (kcals per gram)*
- These are general rules of thumb, the actual values can vary slightly (e.g. a gram of a particular fat may have either 8.8kcals or 9.2kcals). The above numbers are more than accurate enough for macronutrient-tracking.
- *Some soluble fibre also contains kcals although they are of a very small amount.
- Alcohol contains roughly 7kcals per gram.
Why care about macronutrients if weight loss is all about calories?
1. Retention of, or increases in lean body mass.
You do not want your diet to be causing reductions in muscle mass, as this could result in weight loss without an actual decrease in your bodyfat percentage.
Basically this is one of the least desirable situations that can arise from a diet, as the end product if often referred to as “a skinnier version of your fat self”.
A bit harsh perhaps, but essentially you don’t end the process feeling particularly leaner, just slimmer and psychologically/physically worn out from calorie restriction.
A lot of this refers to your protein intake, which should be anywhere from 1.4g-2.2g per kg of bodyweight, depending on your size, muscle mass, exercise regime and so forth.
In some cases this number may be even higher, up to 3g per kg of bodyweight, due to prolonged/extreme caloric restriction and lower body fat levels. Learn more about your protein requirements here.
2. Adherence and enjoyment.
We all have different preferences and it is important for an idividual’s diet to cater to these preferences to promote a healthy & sustainable diet.
After determining one’s minimum protein requirements, the remaining calories are left to be distributed amongst carbs and fats.
Somebody who does not really care for fatty foods but gets a lot of enjoyment from higher carb foods, would shift the ratio to be more in favour of carbohydrates, subject to them hitting their minimum essential fat requirements.
Nobody’s macronutrient ratio should be set in stone, after hitting the minimum requirements for protein, fat, adequate vitamins/minerals etc, there really is a lot of room for freedom – eat in a way that leaves you feeling satiated so that your diet can be enjoyable.
Just health in general really.
Hitting a reasonable amount of fibre lends itself to better gut and colon health.
Adequate fat (particularly saturated fat) intake lends itself to generally higher testosterone (and other sex hormone) levels, which is very important, particularly in men (compared to lower fat diets).
Moderate to high (relatively speaking of course) carbohydrate consumption should help out energy levels both inside & outside of the gym, as well as promoting deeper sleep, and much more.
Balance is very important regarding macronutrients – our diets are responsible for so much more than we care to think regarding our day to day health.
I’ve written an article about setting up your macros for cutting (losing fat), which you can read here.
What about exercise? Should I lift weights, run, swim?
Before I answer this let me just clarify something in case it wasn’t already clear.
You can effectively lose weight without ever doing any intentional exercise, as weight loss comes down to your calorie deficit.
The obvious problem with this is that it requires much lower calorie consumption to lose weight compared to someone who is active and burns more calories per day (higher TDEE). In the interest of adherence, faster results and a better looking end product, exercise is a crucial tool to getting the results you want.
Resistance training (aka lifting weights):
You should all be doing this, and yes that includes you ladies (lifting weights will not make you bulky, this is a myth). Let’s quickly cover the reasons why you should be, in regards to fat loss.
1. That end physique you have in your mind right now? It requires some degree of muscle mass. Whether you’re a female looking for that slender, toned look, or a guy looking for the lean v-taper, slim waist and wide shoulders – you’re not going to get there without having some muscle on your body.
Therefore, it is important that resistance training is incorporated in to your regimen for at least 2 sessions per week. I have an entire area of this website dedicated to training principles and how to make progress which you can view here.
2. Remember earlier we covered what your BMR is? The amount of calories your body burns a day with absolutely 0 activity (aka you being in a coma).
Well, muscle is metabolically active tissue that requires energy just to maintain itself. In other words, increasing your level of muscle mass means that you require more calories per day just to maintain your weight, and fat loss becomes considerably easier with each additional pound of muscle.
3. The actual act of resistance training not only burns calories (as does any exercise), but requires an increased uptake of glucose and can considerably benefit an individual’s insulin sensitivity.
What does this mean? Basically it means your body is more effective at processing elevated blood sugar/glucose levels, and you’re on the path away from diabetes.
Note: Insulin sensitivity is also improved from cardiovascular exercise.
Often broken down in to low intensity (steady state) and high intensity (interval training), the health benefits of cardio are in considerable abundance and I doubt you need me to tell you “cardio is good for your body”. But how does it relate to fat loss?
Let’s be brief and think about this from a purely aesthetic, “I want to look lean for the beach” perspective. We know burning body fat is a result of our calorie deficit, and therefore, cardio is simply another tool of helping you facilitate that calorie deficit.
You can either burn 200 calories on a brisk walk, or you can eat 200 calories less – the effect is going to be pretty much identical (obviously it isn’t entirely identical because the cardiovascular work is going to have an effect on your muscles and insulin sensitivity, but the point is it’s probably minimal, especially as you’re resistance training).
So, in order to promote adherence via being able to eat more calories and feel less starved, I’d recommend gradually implementing more low intensity cardio sessions as your diet progresses (low intensity work does not require additional recovery from the body and can actually aid recovery from resistance training, which is why I promote it over HIIT for fat loss. HIIT still has its place however, particularly for performance/athletic benefits.)
‣You need to consume 2000 calories per day to lose weight, with no cardio.
‣After 2-3 weeks your weight loss begins to slow down due to you becoming leaner & some general metabolic adaptation.
‣You now add in 3 cardio sessions per week burning 100 calories.
‣In 2 more weeks weight loss slows down, you now increase these cardio sessions to 200 calories each.
‣Eventually you lower your calories to 1800, and maintain the cardio.
‣Cardio now increases to 4x per week.
And so forth.
Prolonged dieting may/will require the use of refeed days and potentially even complete diet breaks. You can read more about them here.
Summary – Your complete weight loss plan, just shorter.
• Fat loss comes down to your calorie deficit – you must consume less calories than you expend in order to lose body fat. This is the crucial, underlying logic behind any weight loss plan.
• To work out your daily calories required, calculate your TDEE and then subtract 15-25% from this number (the more fat you have to lose, the closer to the 25%). Use my calculator here to work out your daily calories.
Rule of thumb: 3500 calories = 1lb of actual fat mass, but scale weight loss likely to be different.
• As you lose weight and get leaner, your TDEE will gradually decrease, and therefore so will your daily calories.
• You should consume a good balance of all 3 macronutrients in order to promote adherence, enjoyment, muscle mass retention/gain – else your weight loss may include muscle which results in a poor looking end result. Read more about setting up your macros here.
• Specific food choices & meal timing is not particularly important. Hitting your caloric and macronutrient goals are all that is necessary for effective fat loss.
It is also important to consume adequate fibre and plenty of fruits & vegetables for their micronutrient content.
• Resistance training should be utilised to boost metabolic rate, improve insulin sensitivity and result in a more aesthetically pleasing physique.
Weight loss without resistance training results in muscle loss and can be very difficult to achieve a lean looking body – often results in a “skinny-fat” look. Also requires a far lower calorie intake in the long-run (not fun).
• Use low intensity cardio as a tool to burn more calories as opposed to restricting caloric intake further, i.e. 4x a week 150 calories burned of cardio = 600 additional weekly calories burned.
• Incorporate refeed days and/or diet breaks as necessary – read more about these here.
-  Garthe I, Raastad T, Refsnes PE, Koivisto A, Sundgot-Borgen J. Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. Int J Sport Nutr Exerc Metab. 2011;21:97–104.
-  Hall KD. What is the required energy deficit per unit weight loss? Int J Obes. 2007;32:573–576.
-  Helms E, Aragon A, Fitschen P. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr, 2014, May 12.
Recommended reading ^.
-  Van Der Heijden GJ, Wang ZJ, Chu Z, Toffolo G, Manesso E, Sauer PJ, Sunehag AL. Strength exercise improves muscle mass and hepatic insulin sensitivity in obese youth. Med Sci Sports Exerc, 2010, Nov.