The best macros for sustainable fat loss are 30-35% protein, 35-40% carbohydrates, and 25-30% fat, adjusted to your calorie needs based on age, weight, height, and activity level. Extreme low-carb or high-protein diets produce faster short-term results but have a 95% failure rate beyond 12 months. Sustainable macro splits prioritise adherence over speed.

If you've ever followed a strict diet that worked for a few weeks before becoming unbearable, you already know the problem with extreme approaches. The macros that produce lasting results aren't the ones that push you hardest — they're the ones you can actually stick to. Here's how to find yours.

Key Takeaways

• Sustainable fat loss macros sit at 30-35% protein, 35-40% carbs, and 25-30% fat — flexible enough to maintain long-term
• Extreme diets fail 95% of the time beyond 12 months because they eliminate entire food groups or cut calories too aggressively
• Protein is the anchor: 1.6-2.2g per kg of bodyweight protects muscle mass and keeps you fuller for longer
• Your ideal macros depend on your lifestyle, not a one-size-fits-all formula — use the calculator above to find your starting point

What Are Macros and Why Do They Matter for Fat Loss?

Macros — short for macronutrients — are the three categories your calories come from: protein, carbohydrates, and fat. Each serves a distinct function in your body, and the ratio you eat them in directly affects whether you lose fat, lose muscle, or both.

Protein builds and preserves muscle tissue. Carbohydrates fuel your training and daily energy. Fat supports hormone production and nutrient absorption. Cut any one too aggressively, and your body compensates in ways that stall progress — lower energy, increased hunger, hormonal disruption.

The reason macros matter more than just calories alone: two people eating 1,800 calories per day will get very different results if one eats 40% protein and the other eats 15%. Body composition changes depend on what your calories are made of, not just how many you eat.

Why Do Extreme Diets Fail Long-Term?

Extreme diets fail because they rely on willpower rather than sustainability. Research from UCLA's meta-analysis of 31 long-term diet studies found that 95% of people who lose weight through restrictive dieting regain it within 1-5 years.

The pattern is predictable. You slash carbs to under 50g per day or drop calories to 1,200. The first 2-4 weeks feel productive — you lose 4-8 pounds, mostly water and glycogen. Then hunger hormones spike, energy crashes, and adherence drops.

Metabolic adaptation compounds the problem. Your body reduces its energy expenditure by 10-15% when calories drop too fast, making further fat loss harder with each passing week. When you inevitably return to normal eating, your metabolism is slower than before — and the weight returns, often with interest.

Sustainable approaches avoid this cycle entirely. A moderate 15-20% calorie deficit with balanced macros preserves your metabolic rate, maintains energy for training, and keeps hunger manageable enough to sustain for months rather than weeks.

What Is the Best Macro Split for Sustainable Fat Loss?

The best macro split for sustainable fat loss is 30-35% protein, 35-40% carbohydrates, and 25-30% fat. This ratio supports muscle preservation, training performance, and long-term adherence.

Here's what each range achieves:

• Protein at 30-35% (1.6-2.2g per kg bodyweight): Preserves lean muscle during a calorie deficit, increases satiety by 25-30% compared to lower-protein diets, and has the highest thermic effect — your body burns 20-30% of protein calories during digestion
• Carbohydrates at 35-40%: Fuels resistance training and daily activity, supports thyroid function and hormonal balance, and prevents the energy crashes that derail consistency
• Fat at 25-30%: Maintains testosterone and oestrogen production, supports brain function and mood, and allows flexibility with food choices

These ranges are starting points. Adjust based on how you feel after 2-3 weeks — if energy is low, increase carbs slightly. If hunger is high, increase protein or fat.

How Do You Calculate Your Personal Macro Targets?

Calculate your personal macros in three steps: find your maintenance calories (TDEE), apply a moderate deficit, then divide those calories across protein, carbs, and fat using the sustainable split.

Step 1: Find your TDEE. Use the macro calculator at the top of this page. It uses the Harris-Benedict equation combined with your activity level to estimate how many calories you burn daily.

Step 2: Apply a 15-20% deficit. Subtract 15-20% from your TDEE. For someone maintaining at 2,200 calories, that means eating 1,760-1,870 calories per day. This creates enough deficit for 0.5-1 pound of fat loss per week without triggering aggressive metabolic adaptation.

Step 3: Set your macros. Using 1,800 calories as an example:

• Protein (35%): 158g per day (630 calories)
• Carbs (35%): 158g per day (630 calories)
• Fat (30%): 60g per day (540 calories)

Track for 2-3 weeks, then adjust based on your rate of loss, energy, and hunger levels. The numbers are a starting point, not a prison.

How Much Protein Do You Actually Need to Preserve Muscle?

You need 1.6-2.2 grams of protein per kilogram of bodyweight to preserve muscle during fat loss. For most people, this falls between 120-180g of protein per day.

Research published in the British Journal of Sports Medicine confirmed this range through a meta-analysis of 49 studies involving 1,863 participants. Below 1.6g/kg, muscle loss during a calorie deficit increases significantly. Above 2.2g/kg, additional benefits plateau.

Practical protein sources and their yields:

• Chicken breast (150g cooked): 46g protein
• Greek yoghurt (200g): 20g protein
• Eggs (3 large): 18g protein
• Whey protein shake: 25-30g protein
• Tinned tuna (120g): 30g protein

Spread protein across 3-4 meals rather than loading it into one or two. Research shows 25-40g per meal maximises muscle protein synthesis — eating 80g in one sitting doesn't double the benefit.

Can You Eat Carbs and Still Lose Fat?

Yes — carbohydrates do not prevent fat loss. Fat loss is driven by a calorie deficit, not carb restriction. Keeping carbs at 35-40% of your intake supports training intensity, recovery, and long-term dietary adherence.

The misconception that carbs cause fat gain comes from confusing correlation with causation. People who eat excess calories from highly processed, carb-heavy foods gain weight — but because of the calorie surplus, not the carbohydrates themselves.

In our experience working with hundreds of clients, those who maintain adequate carb intake during fat loss phases train harder, recover faster, and stick to their plan longer than those who cut carbs aggressively. A 75kg person eating 1,800 calories with 35% carbs gets roughly 158g of carbohydrates — enough for oats at breakfast, rice with lunch, and potatoes at dinner.

The key distinction: prioritise complex carbohydrates (oats, rice, potatoes, fruit, vegetables) over refined sugars. Complex carbs digest slower, stabilise blood sugar, and keep you fuller.

How Do You Adjust Macros When Progress Stalls?

When fat loss stalls for 2-3 consecutive weeks despite consistent tracking, make one adjustment at a time rather than overhauling everything. Reduce daily calories by 100-150 through a small carb or fat reduction.

The most common reasons progress stalls:

• Calorie creep: Portion sizes gradually increase without realising. Re-weigh foods for a week to recalibrate
• Metabolic adaptation: Your body has adjusted to the current intake. Drop carbs by 15-20g or fat by 5-8g
• Increased activity compensation: You're unconsciously moving less outside the gym. Track daily steps and aim for 8,000-10,000
• Water retention: Stress, poor sleep, or increased sodium can mask fat loss on the scale. Check waist measurements and progress photos

Avoid the temptation to slash calories dramatically. Dropping from 1,800 to 1,400 creates a 22% deficit that triggers muscle loss and metabolic slowdown. Instead, step down in 100-150 calorie increments every 2-3 weeks. This preserves your metabolic rate and keeps the process sustainable.

Frequently Asked Questions

Do I need to track macros forever to maintain my results?

No. Track macros for 8-12 weeks to build an intuitive understanding of portion sizes and food composition. Most clients transition to flexible eating after this period, checking in with tracking for one week per month to stay calibrated. The goal is education, not dependency.

Is a 40/30/30 split better than 35/35/30 for fat loss?

A higher-protein 40/30/30 split works well for fat loss phases where preserving muscle is the priority. The 35/35/30 split suits people who train at higher intensities and need more carbohydrate fuel. Both produce similar results — the best split is the one you can maintain consistently.

Can I drink alcohol and still hit my macros?

Yes, in moderation. Alcohol contains 7 calories per gram and provides no macronutrient benefit. Account for it by reducing carbs or fat on days you drink. Limit to 1-2 drinks, 2-3 times per week maximum — beyond this, recovery and sleep quality decline enough to noticeably slow progress.

How quickly should I expect to see results with sustainable macros?

Expect 0.5-1 pound of fat loss per week with a sustainable approach. Visible body composition changes typically appear at weeks 4-6. Measurements and how clothes fit change before the scale does. After 12 weeks, most people lose 10-20 pounds of fat while maintaining or gaining muscle.

Should I eat different macros on training days versus rest days?

You can, but it's not necessary for most people. Keeping macros consistent daily simplifies tracking and improves adherence. If you prefer cycling, add 20-30g of carbohydrates on training days by reducing fat by 10g. The difference in results is marginal compared to the added complexity.

What happens if I go over my fat macro for the day?

Going slightly over one macro on a single day has no meaningful impact on your results. Fat loss is determined by weekly and monthly averages, not daily perfection. If you exceed fat by 15g, reduce it slightly the next day or simply continue as normal. Consistency across weeks matters more than precision on any given day.

Are meal replacement shakes a good way to hit my macros?

Meal replacement shakes can supplement your diet when whole food meals aren't practical, but they shouldn't replace more than one meal per day. Whole foods provide fibre, micronutrients, and greater satiety than liquid meals. Use protein shakes strategically — post-workout or as a snack — rather than as dietary staples.

Do macros matter if I'm just trying to lose weight, not build muscle?

Macros matter regardless of your goal. Even if muscle building isn't your priority, adequate protein (1.6g per kg minimum) prevents muscle loss during a deficit. Losing muscle alongside fat lowers your metabolic rate, makes you look less toned at a lower weight, and increases the likelihood of regaining weight.

Your Sustainable Macros Start With the Right Numbers

Sustainable fat loss doesn't require extreme measures. A moderate deficit with balanced macros — 30-35% protein, 35-40% carbs, and 25-30% fat — produces steady, maintainable results without the hunger, fatigue, and rebound that come with aggressive dieting.

Use the macro calculator at the top of this page to find your personalised starting point. Track for 2-3 weeks, adjust based on how your body responds, and focus on consistency rather than perfection.

If you want expert guidance translating these numbers into a plan that fits your lifestyle, our personal trainers build sustainable nutrition and training programmes tailored to your goals.

Book a Free Session →

Sources

• Mann, T. et al. (2007). Medicare's Search for Effective Obesity Treatments: Diets Are Not the Answer. American Psychologist, 62(3), 220-233.
• Morton, R.W. 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, 52(6), 376-384.
• Helms, E.R. et al. (2014). Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition, 11(1), 20.
• NHS — Understanding Calories and Weight Management
• ACSM — Nutrition and Athletic Performance Position Stand

Written by: Revolution PTS Team
Last Updated: January 2026