MyFit@ACU: What should I eat if I'm trying to lose weight?

Published: Wednesday 4th March 2015

MyFit@ACU is an Australian university first; an eight week, online, interactive fitness challenge.

The program has been designed for staff and students with the aim of transforming your health and fitness.


With the MyFit@ACU program well underway, this week's focus, is on eating right in order to meet your weight goals.

The following has been adapted from this week's MyFit@ACU blog entry.

What should I eat if I am trying to lose weight?

Is this a question you ask yourself while fretting over whether to eat a brown rye ham and tomato sandwich, or devour that multigrain chicken and avocado wrap?

I am asked this question at least three times per day and with seven years of answering this question, it hasn't become any easier. There is a wealth of (often confusing) information out there. Should I fast for the next 12 hours to burn fat, drink a meal replacement shake or eat five small meals?

My philosophy about eating pertains to Newtons First Law of Thermodynamics (hold on, don't fall asleep on me yet!), whereby energy is constant.

Don't freak out, you don't need to understand the theory at a PhD level. Here's an example: When you swallow a piece of food, our bodies do their best to convert it to energy that can be used, for example, carbohydrates, fat and muscle are all stores of energy which our bodies need to survive.

In order to maintain, increase or decrease our body weight we need to eat in accordance with what our energy needs dictate. This week’s blog looks at our bodies' kilojoule/caloric needs. In subsequent weeks, I'll then address our bodies' macronutrient needs (carbs, proteins, fats, vitamins, minerals, etc.).

The following formula can be used to understand how many kilocalories you'll need to eat to maintain your same body weight.

The formula we will use here is called the Mifflin St Jeor Equation. It's a revision of the Harris-Benedict Equation (which works out energy needs by weight, height, age, gender and activity level) and is an incredibly accurate measurement tool!

How to calculate your kilocalories

  1. Multiply the number 10 by your body weight in kilograms = Step 1
    Eg 10 x 58 kg = 580 kilocalories
  2. Multiply 6.25 by your height in centimeters = Step 2
    Eg 6.25 x 165 = 1031.25 kilocalories
  3. Multiply the number 5 by your age in years = Step 3
    Eg 5 x 19 = 95 kilocalories
  4. If you are male, add 5 to the combined total of your answers to Steps 1, 2 and 3
    Eg 580 + 1031.25 + 95 + 5 = 1,711.25 calories = your caloric needs if you are sedentary
  5. If you are female, deduct 161 from the combined total of your answers to Steps 1, 2 and 3
    Eg 580 + 1031.25 + 95 – 161 = 1,545.25 calories = your caloric needs if you are sedentary

NB. If you prefer to know your energy intake in kilojoules, multiply your answer after step 4/5 by 4.184. Calories and kilojoules are measures of energy (like kilograms and milligrams for weight) and for every calorie there is 4.184 kilojoules.

Your physical activity level can change how much you need to eat as well, so multiply your calories by the numbers below, which correlate to your level of physical activity.

  • 1 = little to no physical activity
  • 1.2 = 1–3 days of light exercise per week
  • 1.4 = 3–5 days of moderate exercise per week
  • 1.6 = 6–7 days of hard exercise per week 
  • 1.8–2.0 = you train like a beast and have a physical job 5–7 days per week

Eg 1.2 x 1,545.25 calories = 1854.3 calories per day (or 7,758.40 kilojoules).

Now, I recommend reducing your calories slowly over the course of a few weeks or eating more if you're training to gain weight. A helpful approach is to reduce your caloric intake by 400 kilojoules each week until you are eating the right amount for your goal weight (worked out using the equation above).

Happy eating!!

Nathan McLean
Co-founder of MyFit@ACU

For more information, or to access the free MyFit@ACU resources, visit the MyFit@ACU website. Alternatively, contact Nathan McLean via email or by phone on (03) 9953 3665.