So You Want to Lose 20KG? Here’s How I Would Do It. Part 2 of 4.
A Clinical Nutrition Guide to Fat Loss and Muscle Maintenance
Part 2: Applying the Fundamentals
In Part 1, we established that losing 20 kg shouldn't simply be treated as an exercise in making the scales move down as quickly as possible. We defined the objective as reducing excess body fat while preserving as much skeletal muscle, strength and physical function as reasonably possible. We established our baseline, estimated energy requirements, introduced a moderate calorie deficit and discussed why resistance training, daily activity and realistic expectations need to be built into the intervention from the beginning. Most importantly, we stopped looking at 20 kg as one enormous target and instead created smaller checkpoints where progress can be assessed and the intervention adjusted. Now we need to turn that plan into an actual diet.
And this is where things can become unnecessarily complicated.
Low carbohydrate or low fat? Fasting or six meals a day? Keto? Mediterranean? Don't eat after 6 pm? Avoid insulin spikes? Fasted cardio?
Most of this is secondary to a much simpler question:
Can we construct a nutritionally adequate diet that creates a sustainable energy deficit, provides sufficient protein, manages hunger, supports training and is realistic enough to follow for the months required to lose a substantial amount of body fat?
That's what Part 2 is about.
The Calorie Deficit Is the Foundation
Let's start with the least fashionable part of fat loss.
If we're going to reduce stored body energy, we need to establish an energy deficit.
Over a sufficient period of time, energy intake needs to be lower than energy expenditure.
That doesn't mean human metabolism is a simplistic calculator. Energy expenditure can change as body mass falls. Appetite can increase. Spontaneous physical activity can change. Training volume can change and adherence is rarely perfect.
But none of this makes energy balance irrelevant.
It makes managing energy balance more complicated.
This is also why arguments about whether low-carbohydrate, low-fat, intermittent-fasting or Mediterranean-style diets are the “best” diet frequently miss the point.
Different dietary approaches can produce fat loss when they successfully create and sustain an energy deficit.
The important question is therefore not simply:
“Does this diet work?”
It's:
“Can this dietary structure help this particular person maintain an appropriate calorie deficit while meeting their nutritional requirements?”
That's a much more useful question.
Protein Becomes a Priority
If we're intentionally reducing calories while trying to maintain muscle, protein becomes particularly important.
During a calorie deficit, we're asking the body to operate with less available dietary energy while simultaneously trying to preserve metabolically expensive tissue.
This is where protein intake and resistance training work together.
Resistance training provides the stimulus to retain muscle. Protein provides the amino acids required to support it.
For healthy adults undertaking resistance training during a fat-loss phase, I'd generally want protein intake substantially above the minimum intake required simply to prevent deficiency.
In practical coaching terms, somewhere around 1.6–2.2 g of protein per kilogram of body weight per day is often a useful range for resistance-trained individuals, although requirements should be individualised according to body composition, training status, age, total energy intake and clinical circumstances.
For someone with substantial obesity, blindly calculating protein from total body weight can sometimes produce unnecessarily large targets. In those situations, using goal body weight, estimated lean mass or an adjusted reference weight can provide a more practical starting point.
And protein doesn't need to come exclusively from chicken breasts and protein shakes.
A well-constructed diet can include:
Fish, poultry, lean meat, eggs, dairy, Greek-style yoghurt, cottage cheese, tofu, tempeh, soya, beans, lentils, pulses and other appropriate plant proteins.
Protein supplements can also be useful where convenience is required, but they're a tool rather than a requirement.
The important point is consistency.
I'd rather see adequate protein distributed across several meals than someone eating very little protein throughout the day and trying to rescue the target with an enormous evening meal.
Protein Also Helps Us Manage Hunger
Protein isn't only relevant because we're concerned about muscle.
It can also contribute to satiety.
And satiety becomes increasingly important when we're deliberately asking someone to consume less energy than they expend.
A calorie deficit that looks perfect on a spreadsheet but leaves someone ravenously hungry every evening isn't necessarily a particularly intelligent intervention.
This is where meal composition starts to matter.Instead of asking:
“How little food can I eat for 500 calories?”
we can ask:
“How much nutritious and filling food can I construct within those 500 calories?”
That's a very different approach to dieting.
Carbohydrates Don't Need to Disappear
This is one of the areas where fat-loss nutrition has become unnecessarily ideological.
Carbohydrates don't inherently prevent fat loss.
Insulin doesn't magically override energy balance.
And eating fruit doesn't somehow stop your body accessing stored fat.
If total energy intake creates a sustained deficit, body fat can be reduced while consuming a meaningful amount of carbohydrate.
For someone resistance training several times per week, carbohydrates can also support training performance and glycogen availability.
So rather than asking whether carbohydrates should be removed, I'd ask:
Which carbohydrate sources provide the greatest nutritional return within our calorie budget?
That immediately shifts the conversation towards foods such as:
Potatoes, oats, whole grains, rice, legumes, fruit and vegetables.
These foods can provide carbohydrates alongside fibre, vitamins, minerals and—in the case of legumes—meaningful amounts of protein.
That doesn't mean sugar is forbidden.
It doesn't mean you can never eat bread.And it certainly doesn't mean eating a banana at 8 pm suddenly changes the laws of thermodynamics.
It means that when calories are restricted, we want the majority of our food choices to provide something useful in return.
Fruit Absolutely Belongs in a Fat-Loss Diet
Fruit deserves its own mention because it continues to attract completely unnecessary controversy.
Yes, fruit contains sugar.
It also contains water, fibre, vitamins, minerals and numerous bioactive compounds, and whole fruit can be incorporated comfortably into an energy-controlled diet.
A piece of fruit and a confectionery product containing an equivalent amount of sugar aren't nutritionally interchangeable simply because both contain carbohydrate.
This is where reducing foods to individual nutrients becomes misleading.
We eat foods, not isolated molecules.
For someone trying to lose substantial amounts of body fat, fruit can actually be extremely useful because many fruits provide considerable food volume for relatively modest energy intake.
So I'm not removing the apples and berries because they contain fructose.
I'm probably using them.
Dietary Fat Still Matters
If carbohydrates don't need eliminating, neither does dietary fat.
Fat is an essential component of the diet and provides essential fatty acids while supporting the absorption of fat-soluble vitamins.
But fat presents a practical challenge during weight loss:
It's energy dense.
At approximately 9 kcal per gram, relatively small quantities can contribute substantial energy.
This becomes relevant with foods such as oils, butter, nuts, nut butters, cheese, dressings and sauces.
Many of these can absolutely form part of a healthy diet.
But “healthy” doesn't mean calorie-free.
A generous pour of olive oil is still contributing energy even though olive oil can form part of a cardioprotective dietary pattern.
So I wouldn't remove dietary fat.
I'd portion it intelligently.
I'd also generally favour unsaturated fat sources such as olive oil, nuts, seeds and oily fish while limiting excessive saturated fat intake in accordance with established cardiovascular nutrition guidance.
Again, this isn't about banning foods.
It's about constructing the diet around the person's health as well as their calorie target.
Fibre Becomes One of Our Best Tools
Protein gets enormous attention during fat loss.
Fibre deserves considerably more.
Higher-fibre foods can increase food volume, support gastrointestinal health and contribute to satiety while also improving overall dietary quality.
In UK guidance, adults are generally encouraged to consume around 30 g of fibre per day.
For many people beginning a fat-loss programme, simply moving their diet towards more vegetables, fruit, whole grains, beans, lentils and pulses can dramatically change how much food appears on the plate without dramatically increasing calories.
There is, however, no prize for jumping from a very low-fibre diet to enormous quantities overnight.
Increase it progressively.
And drink sufficient fluid.
Your gastrointestinal system will appreciate the courtesy.
This Is Where Eating for Volume Becomes Powerful
One of the biggest differences between a sustainable calorie deficit and a miserable one is often energy density.
Imagine two meals containing roughly similar calories.
One is small, highly energy dense and eaten in six bites.
The other contains lean protein, potatoes, several vegetables and a large salad.
Same calorie budget.
Very different eating experience.
Foods containing more water and fibre can allow us to physically eat a greater volume of food for a given amount of energy.
This is why vegetables become extremely useful.
Not because broccoli burns fat.
It doesn't.But 300 calories worth of vegetables occupies considerably more physical space than 300 calories worth of chocolate.
Potatoes can also be extremely useful.
So can soups.
Fruit.
Salads.
Lean proteins.
Low-fat dairy.
Legumes.
Whole grains in appropriate portions.
We're effectively engineering the diet to make the calorie deficit easier to tolerate.
That's much more useful than simply telling someone to develop more willpower.
Ultra-Processed Foods Need Nuance
This is another area where nutritional discussion often becomes unnecessarily binary.
Not every processed food is nutritionally poor.
Frozen vegetables are processed.
Greek yoghurt is processed.
Tinned beans are processed.
Wholegrain bread is processed.
Protein powder is processed.
The useful distinction isn't simply whether something has undergone processing.The issue is that diets containing large quantities of highly palatable, energy-dense, nutrient-poor foods can make controlling calorie intake considerably more difficult.
Foods engineered around combinations of refined carbohydrates, fats and salt can be very easy to overconsume.
That doesn't mean they must be banned.
A sustainable diet can contain chocolate.
It can contain pizza.
It can contain dessert.
It can contain meals in restaurants.
But if the majority of your calorie budget is being consumed by foods that provide relatively little volume and limited nutritional value, maintaining a meaningful deficit becomes considerably harder.
The goal is therefore not dietary purity.
It's dietary structure.
Build Meals Rather Than Chasing Macros All Day
Once calorie and protein targets have been established, I prefer making the diet increasingly food-focused.
A practical meal might therefore begin with a meaningful protein source.
Add vegetables or fruit.Add an appropriate carbohydrate source.
Include some dietary fat.
Adjust portions according to energy requirements.
For example:
Protein + vegetables + carbohydrate + appropriate dietary fat.
That could be:
Chicken, potatoes, vegetables and olive oil.
Salmon, rice and mixed vegetables.
Lean beef, beans, rice and salad.
Tofu, noodles and stir-fried vegetables.
Greek-style yoghurt, oats, berries and seeds.
The exact foods can change.
The underlying structure remains remarkably consistent.
This also makes nutrition far easier to apply in restaurants, at work or while travelling because the person understands how to construct a meal rather than being dependent on a rigid meal plan.
What About Meal Timing?
For most people trying to lose body fat, total daily energy and nutrient intake matter considerably more than whether breakfast was eaten at 7:00 am or 10:00 am.
Some people enjoy breakfast.
Others aren't hungry in the morning.
Some prefer three larger meals.
Others perform better with four smaller meals.
Meal frequency can therefore be adapted to preference.
But because we're interested in muscle retention, there is a reasonable argument for distributing protein across the day rather than consuming the overwhelming majority in one sitting.
So while I'm not particularly interested in prescribing meals every three hours to “boost metabolism”, I am interested in creating several meaningful opportunities for high-quality protein intake throughout the day.
Again:
Structure without unnecessary rigidity.
Resistance Training Is the Anchor
If there's one form of exercise I don't want disappearing during this diet, it's resistance training.
Cardiovascular exercise is excellent for cardiovascular fitness and can contribute to energy expenditure.
Walking is extremely useful.
But neither should replace the muscular stimulus provided by resistance exercise when muscle retention is a primary objective.
During the fat-loss phase, training doesn't necessarily need to become more complicated.
I'd generally want the person continuing to perform the major movement patterns appropriate to their ability and maintaining meaningful training loads.
The objective isn't necessarily to chase personal bests every week while calories are restricted.
But we want to give the body a persistent reason to maintain strength and muscle.
If training performance is reasonably well maintained as body weight falls, that's useful information.
If strength suddenly collapses across multiple exercises, recovery deteriorates and the person feels exhausted constantly, that's also useful information.
The training programme isn't just burning calories.
It's providing feedback about how well the intervention is being tolerated.
Cardio Is a Tool, Not a Punishment
Cardiovascular exercise absolutely has a place here.
But I wouldn't use it to compensate for eating.
That creates an unhealthy and often unsustainable relationship between food and exercise:
“I ate this, therefore I need to burn it off.”
Instead, cardio should have a defined purpose.
Improve cardiovascular fitness.
Increase physical activity.
Contribute modestly to energy expenditure.
Support health.
The exact amount depends on the person.
Walking is particularly valuable because it's accessible, relatively low fatigue and easy to integrate into normal life.
But again, more isn't automatically better.
If we're performing hard resistance training while in an energy deficit, recovery resources aren't unlimited.
Don't Forget Sleep and Recovery
You can construct an excellent nutritional intervention and still make adherence considerably harder by consistently sleeping five hours per night.
Sleep doesn't violate energy balance, but poor sleep can influence hunger, appetite, food choices, training performance and recovery.
So if someone tells me their diet is becoming increasingly difficult while they're sleeping badly, I'm not automatically cutting another 200 calories.
I want to understand the whole picture.
This becomes particularly important as the diet progresses.
Because the further we move into a substantial weight-loss phase, the more valuable recovery becomes.
What About Alcohol?
Alcohol isn't uniquely capable of preventing fat loss.
But it contributes energy.
At approximately 7 kcal per gram, alcohol can make a meaningful contribution to weekly calorie intake.
Then there are mixers.
And the food eaten alongside it.
And the takeaway on the way home.
And the reduced activity the following morning.
And potentially poorer sleep and training.
For someone drinking several times each week, reducing alcohol intake can therefore create a surprisingly large opportunity to reduce total energy intake without removing much actual food.
That doesn't mean everyone needs complete abstinence.
But alcohol absolutely belongs in the nutritional assessment.
If it contains calories, it belongs somewhere in the calorie budget.
The 80/20 Idea—Used Properly
People often talk about an 80/20 diet.
It's not a clinical formula and there's nothing magical about those exact percentages.
But the underlying concept can be useful.
The majority of the diet should consist of foods that make it relatively easy to meet nutritional requirements while controlling energy intake.
Then leave some flexibility for foods eaten primarily because you enjoy them.
This helps move us away from the idea that a successful diet requires perfection.
Because perfection creates another problem.
Someone eats one unplanned meal and decides they've “ruined the diet”.
They haven't.
One takeaway didn't create obesity.
One salad won't cure it either.
Your habitual dietary pattern is what matters.
What This Might Look Like in the Real World
Let's say our hypothetical individual has an estimated maintenance requirement of around 2,700 kcal and we've established an initial target of approximately 2,200 kcal.
We're not trying to squeeze 2,200 calories into the smallest possible amount of food.
We're trying to obtain the greatest nutritional return from that calorie budget.
Protein is established first.
Meals are then constructed around protein-rich foods, vegetables, fruit, fibre-rich carbohydrate sources and appropriate quantities of dietary fat.
Foods that are very energy dense are portioned rather than necessarily prohibited.
Daily activity is maintained.
Resistance training continues.
Cardio is used where appropriate.
Body weight and waist circumference are monitored.
And then we wait long enough to see what actually happens.
Because the objective isn't to demonstrate how aggressively we can diet.
It's to create an intervention we can still execute several months from now.
Practical Takeaways From Part 2
Keep the calorie deficit at the centre of the intervention. Different dietary strategies can work, but sustained fat loss still requires an energy deficit.
Prioritise protein. For many healthy resistance-trained adults dieting for fat loss, approximately 1.6–2.2 g/kg/day can provide a useful framework, individualised where necessary.
Don't automatically remove carbohydrates. Use carbohydrate sources that support training, fibre intake and overall nutritional quality.
Keep whole fruit in the diet. Fruit provides considerably more than its sugar content.
Include dietary fat—but portion it. Prioritise unsaturated sources while recognising their energy density.
Aim for sufficient fibre. UK guidance recommends approximately 30 g per day for adults, increased progressively if current intake is low.
Eat for volume. Vegetables, fruit, potatoes, legumes, lean proteins and other relatively low-energy-density foods can make a calorie deficit considerably easier to tolerate.
Build meals around food rather than obsessively chasing individual nutrients. Start with protein and construct the rest of the meal around nutritional quality and energy requirements.
Resistance train consistently. Protein provides the building material; resistance exercise provides the reason to retain muscle.
Use cardio strategically. Exercise should improve health and contribute to the intervention—not punish you for eating.
Account for alcohol. You don't have to pretend it doesn't exist simply because the calories are liquid.
Allow flexibility. A diet doesn't need to be nutritionally perfect to be effective.And most importantly:
Build a diet that becomes easier to understand and execute—not progressively more complicated.
The Bottom Line
Once we've established the plan from Part 1, successful fat loss isn't about discovering a secret food combination.
It's about repeatedly executing the fundamentals.
Create an appropriate energy deficit.
Eat sufficient protein.
Resistance train.
Eat plenty of fruit, vegetables and fibre-rich foods.
Choose mostly nutrient-dense foods.
Control the portions of highly energy-dense foods.
Stay physically active.
Sleep.
Recover.
And allow yourself enough dietary flexibility to continue living like a normal human being.
None of those recommendations are particularly exciting.
But that's partly the point.
Effective clinical nutrition is often considerably less dramatic than social media nutrition.
Coming Next — Part 3: Regressive Analysis
Eventually, weight loss is likely to slow.
The calorie intake that worked at the beginning may no longer produce exactly the same result. Body mass has changed. Energy expenditure may have changed. Daily movement may have drifted. Portions may have increased. Training performance may have changed—or perhaps the scales simply haven't moved because of water.
This is the point where many people immediately make the same decision:
Eat less.I
n Part 3, we're not going to do that automatically.
We're going to analyse the data first.
We'll look at weight trends rather than individual weigh-ins, distinguish a genuine plateau from normal fluctuations, reassess energy requirements and activity, audit adherence and use training performance and recovery as additional information.
Only then do we decide whether the intervention actually needs changing.
Because when fat loss slows, the answer isn't automatically more restriction. The answer is analysis.