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Using macros to lose fat or build muscle

If you want to reach your goals, whether they be losing some fat around your hips and thighs, building some serious mass or making it through a weekend without polishing off a weeks worth of food in one sitting, then calculating and monitoring your macros may be the way forward. For more information on what macros are and the scenarios that best fit using this method check this out. For those that hate maths but came here anyway, you may prefer a portion guide and find intuitive eating a better approach.

If you care about changing your body composition then you probably know that diet is key. Whilst there are numerous factors that dictate whether your diet is successful (adherence, environment, effectiveness, sustainability etc.) Two important factors are:

1.Your caloric intake (calories you consume in a day

2. Your macronutrient intake (the amount of protein, carbs and fats)

Obviously we want to optimize our health, hormones, sleep quality, stress levels, micronutrients (vitamins and minerals) but for the purpose of this article lets use macros as the foundation for better body composition and we can focus on the rest later.

There are three main macronutrients, though some would argue the fourth macronutrient is their main source (no judgment)

  1. Protein. (1 gram = 4 calories)

  2. Fat. (1 gram = 9 calories)

  3. Carbs. (1 gram = 4 calories)

  4. Alcohol. (1 gram = 7 calories)

On nutrition labels you will see ‘calories’ that means the combined calories from the above list.

Here’s how to effectively calculate your macros for your goals

STEP 1: Determine your maintenance calories and your goals

There are many formulas to calculate your maintenance calories (the number of calories it takes for your body to maintain your weight and carry out bodily functions).

Use this easy formula

Bodyweight (in lbs) x (12-16) = your maintenance calories

If you are sedentary/ not very active / have a desk job, then shoot for the lower end (12). If you are very active in your day-to-day life, you’re a construction worker and strength train frequently, shoot for the higher end (16). If you are female or want to lose some body fat start with the lower end of 12-13.

If I did not describe you, and you’re disappointed, go for the mid-range of 14.

Remember, these are starting points and may need to be adjusted down the line.

Fat loss example: Sandra, an IT consulatant, weighs 180lbs, is new to the gym and wants to lose fat. She’s sedentary despite going to the gym three times per week. So lets start her off with the lower end of 12.

180lbs x 12 = 2160.

Sandra needs to consume 2160 calories per day to maintain her weight. The idea calorie deficit for most people, who want to lose fat, is between 10-25%. When in doubt, 20% is a good place to start.

20% of 2160 = 432

2160 – 432 = 1728 calories per day to lose fat

Build muscle example: Billy, a 210lb rugby player and University student, wants to gain some size on his upper body for his sport. He strength trains four times per week and is very active. He struggles to put on mass and often skips meals. Billy should start off with the higher end of 16.

210lbs x 16 = 3360

Billy needs to consume 3360 calories per day to maintain his weight. The idea calorie surplus is 200 calories above maintenance, for men, and 100 calories above maintenance for women. This is a rough estimate and may need to be adjusted

3360 + 200 = 3560 calories per day to build muscle

STEP 2: Set your macros

For most people I recommended a 40% protein, 30% fats, 30% carb split to get them started. From there you can adjust based on your preference, hunger levels, activity levels and goals.



Protein intake is crucial for overall health and becomes even more important when we are trying to lose fat whilst preserving muscle. It plays a huge role in hunger and appetite control and the body burns more calories digesting protein than any other macronutrient.

Calculating optimal protein intake

1 .Divide total calories, per day, by 100. For Sandra 1728 calories would equal 17.2. For Billy 3560 calories would equal 35.6

2. Take that number and multiply it by the percentage listed for protein (40%). Sandra 17.2 x 40 = 688 calories. For Billy 35.6 x 40 = 1424 calories

3. Now, divide this number by 4 (calories per gram of protein).

Sandra, 688 / 4 = 172 grams of protein per day

Billy, 1424 / 4 = 356 grams of protein per day


Fats are crucial for health, sex hormones, absorbing fat-soluble vitamins, aiding in digestion, satiety and helping you burn more fat.

Calculating optimal fat intake

Repeat the process above using 30% and divide the values by 9 (calories per gram of fat)

Sandra = 17.2 x 30 = 516 calories

516 / 9 = 57 grams of fat per day

Billy = 35.6 x 30 = 1068 calories

1068 / 9 = 119 grams of fat per day


Carbs are less important for sustaining life and proper function when compared with protein and fats. However, they are still important especially for training, recovery, performance and being a happy, well-adjusted individual. A sure fire way to make someone angry and irritable is to make them do hours of cardio and tell them they can’t eat carbs (I’ve been there).

Calculating optimal carb intake

Repeat the process using 30% and divide the values by 4 (same as protein)

Sandra = 17.2 x 30 = 516 calories

516 / 4 = 129 grams of carbs per day

Billy = 35.6 x 30 = 1068 calories

1068 / 4 = 267 grams of carbs per day

The fine details

I want to add some additional comments to the article. The 40%, 30%, 30% is a rough guide. Some people do excellent on a 30% protein, 55% carbs and 15% fats ratio. Others thrive on 20% protein, 70% fats and 10% carbs. Playing around with your ratios is a good way to know whether a low fat, high fat, low carb, high carb or moderate intake of all three macronutrients is the best approach. You can lose fat on any of these ratios. It’s about finding an optimal ratio that is sustainable for you. Also, know that these ratios can change at any time and being aware of when your body wants is something you should tune into as following popular diets isn't the best approach

You should vary your caloric intake to reflect your activity level. Eat more calories on your training days and reduce calories on non-training days. On training days, eat the majority of your carbs around your workouts and keep fat to the other times of the day.

If you feel hungry, eat more veggies and fiber and ensure you are hitting your protein targets. If you are starving within a few hours of eating a meal this could indicate that you didn’t eat enough protein/veggies or you ate too many carbs. Opt for lean protein, veggies and a good amount of fat (half an avocado and some raw nuts) to start off and adjust from there.

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