Macros for Weight Loss: How to Set Your Protein, Carbs, and Fat

What Macros Are Best for Weight Loss?

The best macros for weight loss are 40% protein, 30% carbohydrates, and 30% fat — with total calories set 300–500 below your maintenance level.

The reason this split works is straightforward. Protein at 40% of total calories (typically 1.6–2.2g per kg of bodyweight) does three things at once: it preserves the lean muscle you have built, it triggers the highest thermic effect of any macronutrient so you burn more calories just digesting it, and it produces stronger satiety signals than carbohydrates or fat. You stay fuller for longer on fewer calories.

Carbohydrates at 30% keep your glycogen stores topped up enough to train hard. This matters more than most people realise. When glycogen runs low, your body breaks down muscle for fuel — the exact opposite of what you want during a fat loss phase. Fat at 30% supports hormonal function: testosterone, oestrogen, and leptin (the hormone that tells your brain you are full) all require dietary fat to work correctly.

In our experience at Revolution PTS, clients who hit a 40/30/30 split consistently outperform those who simply cut calories without paying attention to protein. The number on the scales drops at a similar rate, but the body composition result — how they actually look and how strong they remain — is noticeably better.

Is a 40/30/30 Macro Split Good for Weight Loss?

Yes. The 40/30/30 split is one of the most reliable macro ratios for weight loss because it protects muscle while creating a sustainable calorie deficit.

The science backs this up directly. A meta-analysis in the British Journal of Sports Medicine found that protein intakes of 1.6–2.4g per kg during calorie restriction produced significantly better muscle preservation and greater fat loss compared to standard lower-protein diets. The people eating more protein were losing more fat per kilogram of total weight lost.

We have seen this play out consistently across our London studios. Clients on a 40/30/30 split maintain 85–95% of their training strength during a cut. Those on traditional low-calorie diets with no attention to protein often lose 15–25% of their strength — which means they are losing muscle, not just fat. Losing muscle slows your resting metabolic rate, which is exactly why so many people regain weight after a diet ends.

The 40/30/30 split also makes the deficit easier to sustain. High protein is significantly more satiating than an equivalent number of calories from carbohydrates or fat, so you hit your calorie target without feeling deprived. That is not a small advantage — sustainability is the single biggest variable in any fat loss plan.

What Is the 3-3-3 Rule for Fat Loss?

The 3-3-3 rule for fat loss is a simplified eating framework: three meals per day, three macronutrients tracked per meal (protein, carbs, fat), and a three-hour gap between eating windows.

It is not a scientifically established protocol in the same way as TDEE-based macro tracking, but it works as a practical structure for people who find full macro counting overwhelming. The three-hour eating gap discourages unnecessary snacking, the three-meal structure prevents the constant grazing that inflates calorie intake without you noticing, and tracking three macronutrients (rather than just calories) keeps protein intake high.

The limitation is precision. Without knowing your TDEE and setting specific gram targets for each macro, you are guessing at your protein intake. For someone whose primary goal is body recomposition — losing fat while keeping muscle — that guesswork is where results slip.

Our recommendation: use the 3-3-3 rule as a starting framework to build consistency, then add specific macro targets once you have established the eating pattern habit. Structure first, precision second.

What Is the 40-40-20 Rule for Macros?

The 40-40-20 rule means 40% of your calories from protein, 40% from carbohydrates, and 20% from fat. It is popular in bodybuilding circles and suits people with high training volumes.

The higher carbohydrate allocation (40% vs. 30% in a standard 40/30/30 split) supports more intensive training. If you are training five or more times per week with heavy resistance work, your glycogen demand is substantially higher, and extra carbohydrates improve performance, reduce fatigue, and speed up recovery between sessions.

The trade-off is the 20% fat allocation, which sits at the lower end for long-term hormonal health. For most people training three to four times a week, 40/40/20 provides more carbohydrates than their training actually requires, and the lower fat intake can affect hormonal function over extended periods.

Our guidance: if you train three to four times per week, 40/30/30 is more appropriate. If you are training daily with high-volume sessions — multiple compound lifts, conditioning work, or sport — 40/40/20 becomes the stronger choice. Both splits outperform any low-protein approach for body composition.

How Do You Calculate Your Macros for Weight Loss?

Calculating your macros for weight loss takes four steps: find your TDEE, set your calorie deficit, apply your macro split, then adjust based on real results.

Step 1: Calculate your TDEE. Use the Mifflin-St Jeor equation. For a 75kg male, 30 years old, 175cm, training three to four times per week, TDEE is approximately 2,600 calories per day. For a 65kg female, same age and height, same activity level, TDEE is approximately 2,100 calories.

Step 2: Set your deficit. A deficit of 300–500 calories per day produces 0.3–0.5kg of fat loss per week — the range that protects muscle best. Using the 75kg male example: 2,600 – 400 = 2,200 calories per day.

Step 3: Apply the 40/30/30 split. At 2,200 calories: 40% protein = 880 calories = 220g protein. 30% carbohydrates = 660 calories = 165g carbs. 30% fat = 660 calories = 73g fat. These are your daily gram targets.

Step 4: Adjust every three to four weeks. If you are losing more than 1kg per week, add 200 calories (primarily from carbohydrates or fat) to slow the rate and protect muscle. If you are losing less than 0.25kg per week after four weeks of consistent tracking, reduce calories by 150–200. Never reduce protein — that is the macro that does the most protective work during a deficit.

We walk every Revolution PTS client through this calculation in their first session. It takes under ten minutes and removes all the guesswork from the nutrition side of their programme.

Do Macros or Calories Matter More for Fat Loss?

Both matter, but they do different jobs. Calories determine whether you lose weight at all; macros determine what kind of weight you lose.

Here is the honest explanation. You cannot lose body fat without a calorie deficit — that is thermodynamics and it does not have exceptions. But two people eating the same 2,000 calories per day can have very different outcomes depending on how those calories are distributed across protein, carbohydrates, and fat.

Person A eats 2,000 calories with 40% protein (200g). Person B eats 2,000 calories with 15% protein (75g). Both lose weight. But Person A preserves significantly more muscle, burns more calories through digestion (thermic effect), and experiences less hunger. Person A is losing mostly fat. Person B is losing a meaningful proportion of muscle, which will slow their metabolism and make the weight easier to regain.

Track both. Set your calorie target first — that is the ceiling. Then use your macro split to optimise what happens inside that ceiling. The clients we work with at Revolution PTS who track both consistently achieve noticeably better body composition results than those tracking calories alone, even when the total calorie numbers are identical.

How to Track Macros Without Overcomplicating It

The single most effective thing you can do is use a food tracking app and a kitchen scale for the first four weeks. After that, most people have developed enough intuition about portion sizes to be less rigorous.

For apps, MyFitnessPal and Cronometer are the two most reliable options. Both have large food databases including UK supermarket products and restaurant chains. Set your macro targets in grams (not percentages) and log everything — including cooking oils, sauces, and drinks. These are the four categories that consistently blow calorie budgets without the person realising it.

The kitchen scale is non-negotiable for the first month. Portion estimates are notoriously inaccurate. Research shows people underestimate their calorie intake by 20–40% when guessing portions. That is 400–800 calories at a 2,000-calorie target — enough to eliminate your entire deficit and explain why “eating healthy” without tracking produces no visible results.

Prioritise protein first at every meal. Build your plate around your protein source — chicken, fish, eggs, Greek yoghurt, cottage cheese, lean beef — then fill in carbohydrates and fat around it. This one habit alone pushes most people 80% of the way to a good macro split without obsessive tracking.

After four weeks of consistent tracking, you will know instinctively what 200g of chicken looks like, roughly how many grams of oats fill your bowl, and which meals sit comfortably within your targets. That is the point where tracking becomes low-effort maintenance rather than a daily project. We have found the four-week investment pays off for virtually every client who commits to it.

Get Your Macro Plan Right the First Time

Macro tracking is the most precise tool available for body composition — but it works best when built around your specific training load, lifestyle, and goal. The 40/30/30 split is the right starting point for most people, but the gram targets need calibrating to your actual TDEE and adjusting based on real results over time.

At Revolution PTS, our personal trainers work with you on both your training programme and your nutrition targets — because what you eat determines 60–70% of your body composition results. Our studios in Angel, City, and Holborn serve professionals across London who want to get this right, properly, without guesswork.

Book your complimentary session today and get your personalised macro targets and training plan in one session.

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Written by: Revolution PTS, Personal Training Studio, London
Last Updated: March 2026