Nutrition Essentials Pt 2: How to Lose Fat and Build Muscle
Home / Nutrition / Nutrition Essentials Pt 2: How to Lose Fat and Build Muscle

Nutrition Essentials Pt 2: How to Lose Fat and Build Muscle

To achieve any body composition goal – whether it’s to lose fat, gain muscle or maintain your weight – you need to have the right nutrition. This will play the largest role in determining how you look. If your body isn’t getting the appropriate nutrition, you simply won’t be able to achieve your body composition goals.

If you want to gain or retain muscle, strength training will be the stimulus. Strength training is what breaks down muscle fibres. After you leave the gym, the body then uses the nutrients gained from your meals, and rest, to repair and build muscle size and strength [1]. If you don’t have adequate nutrition or rest, your body will not have what it needs to repair and build muscle.

Likewise, if your goal is to lose fat, you need to be in a calorie deficit. This means you need to be eating less calories than your body uses, but it doesn’t stop there. If your muscles are not getting adequate protein and you are in a calorie deficit, you may lose weight, but it will likely be from muscle, instead of fat. This means you may be missing out on the extensive health benefits of strength training.

If your goal is to maintain your body composition, the key is to consume the number of calories your body needs (which is referred to as maintenance calories), and the right balance of macronutrients. If you’re unsure about what macronutrients are, check out Nutrition Essentials Part 1: Macronutrients & Micronutrients.

Regardless of your goal, you need to work out how many calories you will need to eat each day and eat adequate protein for your bodyweight. Then you need to base your meals and snacks around your remaining nutritional needs to achieve your desired composition.

Calculating calories to lose fat or gain muscle

Calories are the most important factor in making a diet successful. To work out how many calories your body needs at rest, you need to find your BMR (basal metabolic rate).

You can calculate your BMR using the following formula:
Woman BMR = bodyweight in kilograms x 22
(Example for a 60kg female BMR: 60kg x 22 calories = 1,320 calories at rest)
Men BMR = bodyweight in kilograms x 24
(Example for a 90kg male BMR: 90kg x 24 calories = 2,160 calories at rest)

Next, you need to calculate TDEE (Total Daily Energy Expenditure) which takes into account the energy burnt on a daily basis through your daily activities such as walking the dog and work.

You can roughly calculate TDEE using the following:
Sedentary = BMR x 1.2
Moderately Active = BMR x 1.5
Very Active = BMR x 1.8
Athlete = BMR x 2

Now, you will have your maintenance calories, that is, how many calories your body will need to maintain the same composition.

If you want to gain muscle, a slight calorie surplus of 5-10% will be needed.
If you want to lose fat, a calorie deficit of 10-30% will be required.

Or, if you want an online calculator to do the math for you, see

How to work out your macros

Macronutrients (or macros) consist of protein, carbohydrates and fat and are required by the body in different amounts to perform various functions. Macros will make up your total caloric intake and are measured in grams. One gram of protein or one gram of carbohydrates equal 4 calories, whereas one gram of fat equals 9 calories.

When you are setting individual macros, you should ideally first establish your protein target. Protein is an essential nutrient that your body needs to grow and repair cells and is important for satiety [2]. Protein should be set between 1.6-2.5g per kg of bodyweight. If you are starting out in strength training, set your protein towards the lower end and if you are more advanced, towards the higher end.

Fats are the next essential macronutrient and are important for good health. They help the body absorb vitamin A, D, E & K. Fats protect vital organs, assist cognitive function and are essential for hormone production and balance. [3]. At Plexus, we have found most people respond best with fats set around 0.9g-1.2g per kg of bodyweight. However, this will depend on personal preference.

The remainder of calories can then be made up of carbohydrates, which the body uses for energy [4].

Putting it together

How do all these calculations come together? Let’s use an example of a 70kg female. She is moderately active, doing two strength training sessions per week and walks her dog daily.

We can calculate her BMR using the calculation: 70kg x 22 = 1,540kcal BMR at rest
We can find her TDEE by doing the following: BMR = 1,540kcal x 1.5 (activity levels) = 2310kcal

If her goal was to gain weight, she would need to eat a 5% surplus on her maintenance calories, which would be 2,425kcal. We would recommend a daily intake of 130g protein, 90g fat and 281g of carbohydrates.
If she wanted to lose weight, we would recommend a 20% calorie deficit, of 1,848kcal. However, anywhere between 10-30% could be a suitable start, depending on her current body composition and how quickly she wanted to lose weight. We would also recommend a macronutrient intake of 120g protein, 60g fat and 214g carbohydrates.

What does this look like in a meal plan?

The diet of someone who is in a calorie deficit, shouldn’t look that different to someone in a surplus. Eating “clean” does not necessarily equal the correct calorie intake for your goal or energy needs. The difference will come down to the quantities you eat.

Here is an example of a daily intake of what this 70kg female might eat if she wanted to maintain weight:
Breakfast: 2 large eggs, 2 slices GF toast, 30g spinach and 20g cheddar cheese
Lunch: 150g chicken breast, 60g rice (uncooked weight), 100g carrots, 100g celery, 100g cucumber and 5g balsamic vinegar
Afternoon tea: 150g plain low-fat yogurt, 100g blueberries, 100g kiwi fruit and 100g apple
Dinner: 150g lean beef, 250g potato, 100g green beans, 10g butter and 10g olive oil
Snacks: 100g banana, 40g dark chocolate, 20g macadamia nuts, 20g rice cakes and 20g cheddar cheese

If she wanted to lose weight we would recommend is reducing the potato at dinner to 200g and limiting snacks to a smaller, 90g banana and 20g dark chocolate. This would cut out the remaining snacks of macadamias, rice cakes and cheddar cheese.

On the other hand, if she wanted to gain weight, we would tweak the maintenance diet by increasing the rice at lunch to 80g and the potato at dinner to 300g.

Note that on all variations, we have included a little dark chocolate. At Plexus, we believe that provided you’re meeting your micronutrient needs (remember, you can read about micronutrients here), it’s okay to have a bit of food which has less nutritional value to satisfy cravings. If you have a fully restrictive diet, it can be difficult to stick to and lead to 2,000 calorie binges (such as eating an entire pizza and drinking a bottle of wine).

Should I try and lose fat over Christmas?

As we approach the festive season, it’s important to remember that good health is all about balance. It’s okay to enjoy your Christmas lunch guilt-free, but don’t make it a habit. How you approach the Christmas season comes down to your goals. For example, if you are concerned about your weight but want to enjoy a big lunch, you could balance it out with a small breakfast or dinner. Remember to enjoy the time with family and friends and eat slowly.

Read part three of our Nutrition Essentials series

Nutrition Essentials Pt 3: How to Track Calories and Macros