Sustainable Strength nutrition
What to eat, and why it works
Protein, carbs, fats, fibre, water and timing, explained properly. Here's what each one does inside your body, how much you need, and how to turn it into meals without scales, apps or guilt.
I know roughly what I should eat. I just don't know why it matters, so I never stick to it.
I hear some version of this every week in the studio. It makes complete sense. Rules without reasons don't last. You follow them until life gets busy, and then you drop them.
Once you understand what a food is actually doing for you, the decision gets easier. You're not choosing eggs over a pastry because a list told you to. You're choosing them because you know they'll keep you full until lunch, protect the muscle you're working hard to build, and stop you raiding the cupboard at 6pm. That's what this guide is for.
It's long, so here's the map.
Start here
Not everything matters equally
Most nutrition confusion comes from treating every detail as if it carries the same weight. Online, the timing of your banana gets as much airtime as whether you eat enough protein. It shouldn't. Here's roughly how much each factor affects your results, from biggest to smallest.
- 01Energy balanceHow much you eat relative to what you burn. This decides whether you lose, gain or maintain weight.
- 02ProteinThis decides whether the weight you lose or gain is fat or muscle.
- 03Food quality and fibreThis covers health, hunger, energy and digestion.
- 04Meal timingUseful around training and for managing hunger, but it only fine-tunes things.
- 05SupplementsA handful are genuinely useful. None of them can rescue the four above.
If you're struggling, the answer is almost always higher up the list than you think. Get the top two consistent and most people see real change within weeks.
01 · Energy balance
Calories are the budget, not the whole story
Every food contains energy, measured in calories. Protein and carbohydrate provide about 4 kcal per gram, fat about 9, and alcohol about 7. Your body spends that energy on four things: keeping you alive at rest, digesting food, deliberate exercise, and all the everyday movement in between. That last one is walking the dog, the school run and fidgeting at your desk.
Eat more than you spend and the surplus gets stored. Eat less and your body draws on its stores. That part isn't up for debate. It's physics, and every diet that has ever worked, from keto to fasting to "clean eating", has worked by creating a deficit, whether the people following it realised or not.
Where people go wrong is concluding that only calories matter. Two diets with identical calories can feel completely different. One leaves you starving, flat in training and losing muscle. The other keeps you full, strong and consistent. What decides which one you get is what those calories are made of.
The science bit
Your body burns energy just digesting food, which is called the thermic effect of food. It isn't the same for every nutrient. Protein costs far more to process than carbs or fat, so a higher-protein diet gives you a small built-in advantage.
- 20–30%
- of protein calories burned in digestion
- 5–10%
- of carbohydrate calories
- 0–3%
- of fat calories
Quality affects the budget too. In a tightly controlled NIH study, people offered ultra-processed meals ate about 500 kcal a day more than when they were offered minimally processed meals. The meals were matched for the nutrients on offer, and people could eat as much as they liked. Nobody was trying to overeat. The food simply made it easy. It's one of the clearest demonstrations that food choice drives intake without you noticing.
What this means for you: you don't need to count calories to manage them. Build meals around protein, veg and whole foods, and your appetite does most of the counting for you. The hand-portion system later in this guide is designed to do exactly that.
02 · Protein
The one number that never moves
Whether your goal is fat loss, strength or just feeling better, protein is the nutrient I'd fix first. Here's why.
It's the raw material for muscle
Your muscles are constantly being broken down and rebuilt. Resistance training tips that balance towards building, but only if there's enough amino acid supply, and amino acids come from protein. The process is called muscle protein synthesis. A meal with enough good-quality protein switches it on for a few hours.
One amino acid, leucine, acts as the main trigger. Research suggests you need roughly 2–3g of leucine in a meal to get a strong response. That's about what you get from 25–40g of protein from sources like eggs, meat, fish, dairy or whey. Plant proteins work too. You generally need a bit more, or a mix of sources, to reach the same threshold.
It protects muscle when you're losing fat
In a calorie deficit your body looks for energy wherever it can find it, and that includes muscle. Keep protein high and keep lifting, and you send a clear signal to hold on to muscle and draw from fat stores instead. That's the difference between getting leaner and just getting smaller. More muscle also means a body that's stronger, more resilient and burns slightly more energy at rest.
It keeps you full
Protein is the most filling of the three macronutrients. It raises satiety hormones such as GLP-1 and PYY, and it suppresses ghrelin, the hormone that drives hunger. In practice, a protein-rich breakfast leads to fewer cravings and less snacking later in the day. This is exactly the mechanism behind what I call the 6pm wall, which we'll come back to.
It matters more as you get older
From our 40s onwards, muscle becomes a little less responsive to protein. Researchers call this anabolic resistance. It means you need a slightly bigger dose per meal to get the same effect. For busy parents and professionals in midlife, spreading good portions of protein across the day is one of the best investments you can make in how you'll move at 70.
- 1.6 g/kg
- per day: the point where muscle gains level off for most
- 0.4 g/kg
- per meal, across 3–4 meals
- 25–40g
- per meal, for most adults
- 1 palm
- ≈ 20–30g protein
That 1.6 g/kg figure comes from a large 2018 meta-analysis of 49 trials. Some people, especially those dieting hard or training heavily, benefit from going up towards 2.2 g/kg. For a 70kg person that's about 110–155g a day. You don't need to weigh anything to get there. A palm-sized portion at each meal, and two for most men, gets the majority of people into the right range.
Best sources: eggs, chicken, turkey, lean beef, fish and seafood, Greek yoghurt, skyr, cottage cheese, whey or plant protein, tofu, tempeh, edamame, and lentils and beans (these carry plenty of carbs too).
03 · Carbohydrates
Fuel, not the enemy
Carbs have had a rough couple of decades. Here's what they actually do.
They're your main training fuel
Carbohydrate is stored as glycogen, roughly 400g in your muscles and around 100g in your liver for a typical adult. Hard efforts rely heavily on glycogen. That includes heavy sets, circuits and anything that gets you breathing hard. When stores run low you feel flat, you lose output, and sessions feel harder than they should. Your brain also runs mainly on glucose, getting through something like 120g a day, which is part of why very low-carb days can leave you foggy and short-tempered.
Liver glycogen also drops overnight. That's why a small, quick carb snack before a 6am session can make such a difference to how strong you feel.
They don't make you gain fat on their own
When energy intake is matched, high-carb and low-carb diets produce very similar fat loss in controlled studies. Low-carb diets often show a faster drop on the scales in the first week or two. Much of that is water, because each gram of stored glycogen holds around 3g of water. It isn't extra fat loss. Carbs become a problem when they arrive in large amounts of highly processed, easy-to-overeat food, and that's a food-quality issue rather than a carb issue.
Quality changes how you feel
Refined carbs on their own, like a white toast breakfast, a cereal bar or a pastry, digest quickly. Blood glucose rises fast and can dip just as fast, and the dip often shows up as tiredness and cravings. Whole-food carbs such as oats, potatoes, rice, wholegrain bread, beans and fruit come packaged with fibre and water. Paired with protein and a little fat, they release energy more steadily.
The science bit
How much a meal raises your blood sugar depends on the whole meal, not just the carb in it. Adding protein, fat and fibre slows how quickly your stomach empties, which blunts the spike. That's why toast with two eggs behaves so differently from toast alone, even though the carbohydrate is identical.
- 1 cupped hand
- ≈ 20–30g carbs
- More
- on training days and around sessions
- Less
- on rest days, if fat loss is the goal
Best sources: oats, potatoes and sweet potatoes, rice, wholegrain bread and pasta, quinoa, beans and lentils, and fruit. Around training, faster options like bananas, rice cakes and honey have their place.
04 · Fats
Small portions, big jobs
Dietary fat is essential, which means your body can't make certain fats itself and you have to eat them. Fat builds the membrane of every cell in your body, carries the fat-soluble vitamins A, D, E and K, and is the raw material for hormones, including the sex hormones that affect mood, recovery and libido. Drop fat too low for too long and those systems suffer. Studies show that very low-fat diets can modestly lower testosterone in men.
The reason fat portions are kept small is simply energy density. At 9 kcal per gram, fat adds up quickly. A generous glug of olive oil or a few handfuls of nuts can quietly add 300–400 kcal to a day. Nothing is wrong with these foods. They just need a measure.
Omega-3s deserve special mention
The long-chain omega-3 fats EPA and DHA, found mainly in oily fish, play a role in heart health, inflammation, and brain and eye function. Most people in the UK don't eat enough of them. The NHS recommends two portions of fish a week, one of them oily, such as salmon, mackerel, sardines, trout or herring.
05 · Veg, fruit and fibre
The quiet workhorse
Veg won't make headlines, but it does a remarkable amount of work.
Fibre feeds your gut
The UK recommends 30g of fibre a day. The average adult manages around 20g. Fibre that reaches your large intestine feeds your gut bacteria, which ferment it into short-chain fatty acids. These compounds help maintain the gut lining and are linked to better blood sugar control and lower inflammation. Higher fibre intakes are consistently associated with lower rates of heart disease, type 2 diabetes and bowel cancer.
Volume keeps you full for fewer calories
Veg is mostly water and fibre, so it has a very low energy density. Research on energy density shows that people tend to eat a fairly consistent volume of food. Filling part of that volume with veg means you feel just as full on fewer calories, without trying to eat less. This is the least painful fat-loss tool there is.
Micronutrients you can't skip
Magnesium, potassium, folate, vitamin C, vitamin K and a long list of plant compounds all come mainly from fruit and veg. Low levels won't show up overnight, but they show up in energy, sleep, recovery and long-term health. Variety matters more than any single "superfood", so aim for different colours across the week.
- 1 fist
- of veg or salad at each meal
- 30g
- fibre per day (UK target)
- 30+
- different plants a week is a great stretch goal
06 · Hydration
Being slightly dry costs you more than you'd think
Losing as little as 2% of your body weight in fluid, about 1.4 litres for a 70kg person, is enough to measurably reduce performance and make hard work feel harder. It also affects concentration and mood, and thirst is easily mistaken for hunger in the afternoon.
You don't need to track millilitres. A few habits cover most people.
Your hand is the measure
No scales. No apps. Just your hand.
Here's how everything above turns into a meal. Your hand is always with you, and it's roughly proportional to your body size. Bigger people have bigger hands and need bigger portions. It isn't perfectly precise, but it's consistent, and consistency is what gets results.
Protein
Eggs, chicken, fish, lean meat, Greek yoghurt, tofu, whey
Carbs
Rice, oats, potato, bread, pasta, beans, fruit
Veg
Salad, greens, peppers, broccoli, carrots, anything colourful
Fats
Oil, butter, nuts, nut butter, cheese, avocado
That's one meal portion for most women. Most men double it. Eaten three to four times a day, it's a solid starting point for the majority of people. Then you adjust based on what actually happens, not on what a calculator predicts.
Mixed dishes like a curry, a stew or a pasta bake are fine. Just estimate roughly how much of each part is on the plate. You're aiming for good enough, not perfect.
Adjusting for your goal
Same foundation, different dials
The plate above stays the same. What changes is how much of it you eat, and where. Adjust one thing at a time, give it two weeks, then review your weight trend, waist measurement, energy and training. Your body's response is the best data you'll ever get.
Fat loss
Keep protein and veg fixed. They protect muscle and hunger. Take out one cupped hand of carbs or one thumb of fats per day. Losing about 0.5–1% of body weight a week is a pace you can keep up without losing strength.
Strength and muscle
Push protein towards the top of the range, and put most of your carbs around training to fuel the work and refill glycogen. If you're not gaining strength and your weight isn't moving, add a cupped hand of carbs a day.
Energy and health
Protein at every meal, a fist of veg twice a day, and fewer ultra-processed snacks. For many busy people this alone clears up the afternoon slump and the evening grazing, and weight often follows.
07 · When to eat
Timing fine-tunes. It doesn't fix.
You'll often hear that you must eat within 30 minutes of training or you've "wasted" the session. The research doesn't support that. When studies on protein timing are pooled together, the benefit mostly disappears once total daily protein is matched. The window around training is more like several hours than several minutes. Where timing does help is in how you spread your food and how you feel.
Spread protein across the day
Most people eat a small breakfast, a moderate lunch and most of their protein at dinner. One study compared that pattern with the same total protein spread evenly across three meals of about 30g each. The even pattern produced roughly 25% more muscle protein synthesis over 24 hours. Three to four protein-rich meals beat one big one.
Around your sessions
The 6pm wall starts at breakfast
If you're "good all day" and then eat everything in sight once you're home, it isn't a willpower problem. It's usually a morning built on coffee, or toast on its own, followed by a carb-heavy lunch. That means low protein, unsteady blood sugar and rising hunger hormones, all meeting you at the front door. Get 25–30g of protein into breakfast, keep protein at lunch, and the evening often sorts itself out.
Simple swaps
Toast alone → toast and 2 eggs. Cereal → Greek yoghurt, fruit and granola. Coffee only → coffee and a protein shake. Each of these swaps adds about 20–25g of protein and takes no extra time.
08 · Supplements
A short list, on purpose
The supplement industry needs you to believe the answer is in a tub. It rarely is. There are a handful with strong evidence, and they only matter once the basics are in place.
If you're pregnant, breastfeeding, managing a medical condition or taking medication, check with your GP or pharmacist before starting any supplement.
Myths, quickly
Things you can stop worrying about
“Carbs after 6pm turn to fat.”
Your body doesn't check the clock. Total intake across the day is what matters. A carb-based evening meal can even help some people sleep better.
“You can only absorb 30g of protein at once.”
You absorb nearly all of it. Larger doses are just used over a longer period. 30–40g per meal is a useful target, not a ceiling.
“Fasted training burns more fat.”
You burn more fat during the session, and your body balances it out across the day. Over weeks, fat loss is the same when calories are equal. Do what makes you feel strongest.
“You need to detox.”
Your liver and kidneys do that full-time, for free. Support them with fibre, water, sleep and less alcohol. You don't need juices.
“Healthy eating means cutting out foods you love.”
Rigid rules backfire and lead to all-or-nothing swings. Aim for roughly 80% whole foods and enjoy the rest without guilt. That's what sustainable looks like.
Making it stick
Practise skills, not rules
Knowing all of this is step one. The real work is turning it into things you do on a Tuesday when the kids are ill and work is on fire. That takes practice, not willpower.
So don't change everything on Monday. Pick one habit, the one you're about 90% sure you can do every day for the next two weeks, and practise it until it's boring. Then add the next one.
- 01A palm of protein at breakfastThis is the biggest single lever for hunger and the 6pm wall.
- 02A palm of protein at every mealThis spreads muscle protein synthesis across the day.
- 03A fist of veg at lunch and dinnerFibre, volume and micronutrients with almost no effort.
- 04Hand portions for carbs and fatsThis is where you start steering energy balance towards your goal.
- 05Review every two weeks and adjust one dialLet your results decide the next change.
Sustainable beats perfect. Every time.
“Food is fuel. Eat enough protein, eat your veg, portion the rest with your hand, and give it time. No extremes, no guilt, just a simple system you can keep for life.”
Want your portions set for your body and your goals?
This guide gets you most of the way. Coaching gets you the rest. We set your portions, fit them around your training, your job and your family, and adjust as you progress. It happens 1:1 at our Northwood studio or online.
Start your Sustainable Strength coachingKey research referenced
- Morton RW et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength. British Journal of Sports Medicine.
- Schoenfeld BJ, Aragon AA (2018). How much protein can the body use in a single meal for muscle-building? Journal of the International Society of Sports Nutrition.
- Mamerow MM et al. (2014). Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. Journal of Nutrition.
- Schoenfeld BJ, Aragon AA, Krieger JW (2013). The effect of protein timing on muscle strength and hypertrophy: a meta-analysis. JISSN.
- Leidy HJ et al. (2015). The role of protein in weight loss and maintenance. American Journal of Clinical Nutrition.
- Hall KD et al. (2019). Ultra-processed diets cause excess calorie intake and weight gain. Cell Metabolism.
- SACN (2015). Carbohydrates and Health. Public Health England.
- Rolls BJ (2009). The relationship between dietary energy density and energy intake. Physiology & Behavior.
- American College of Sports Medicine (2007). Exercise and fluid replacement: position stand.
- Kreider RB et al. (2017). ISSN position stand: safety and efficacy of creatine supplementation.
- NHS. Vitamin D guidance; Fish and shellfish guidance.