Five nutrition mistakes you make when you start exercising

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  • Eating the right foods when exercising regularly goes hand in hand with improving our health
  • However, often there are diet mistakes we make along the way that can undermine our workouts, and even be bad for our bodies
  • A dietitian provides key tips to avoid making such mistakes

We are living in an age of abundant information – and finding out if you are eating adequately and correctly in conjunction with exercise can be overwhelming and often confusing.

We have summarised a few keys points to consider when you start exercising:


Research has shown that most people overestimate the energy their bodies need for the activities they're performing.

The additional energy you need depends on the frequency, intensity, and duration of the activity you choose. This often leads to people consuming too much energy (kilojoules) for what they are burning or what their body needs for the day.

It is, therefore, important to remember that those of us who take part in recreational exercise three to fives times per week for a period of 30 to 60 minutes do not need to eat much more than we usually do.


On the opposite end, some people tend to undereat because they are trying to achieve their weight loss goal as quickly as possible.

They restrict their energy intake and push themselves harder to burn more energy. The problem with this practice is that your body still needs energy to sustain vital functions such as heartbeat, breathing and many other metabolic processes.

Consequently, if you exercise at a high intensity for long and fail to replenish this shortfall with food, your body will start to break down muscle to meet its energy needs. This is the opposite of what you are wanting to achieve. 

Focusing on supplementation

There seems to be a need for some people to use supplements as soon as they start to exercise. This may be due to the advice on fitness and health that promotes supplements, convincing you that you need to be supplementing.

Supplements (additional kilojoules, protein, carbohydrates, minerals, or vitamins) do serve a purpose. They are often given to athletes that cannot meet all their nutrient requirements via food. They are training at such an intensity, frequency, and duration that their nutritional requirements cannot be met by their daily food intake. 

For these individuals, adding the additional nutrients in a shake makes it easier to avoid feeling overly full. If you are doing exercise for recreational reasons or are slowly starting to work towards your 150 minutes of exercise per week (general health recommendation), there should be no need for supplementation. 

Eating 'whatever you want' because you are doing exercise

Another common mistake people make is to think that they can eat whatever they want after exercise because the exercise will make up or cancel out the energy (kilojoules) supplied by the food. This is a misconception. Unfortunately, no matter how much you exercise, you cannot “out-exercise a bad diet”.

Also, if you "replenish" your body with foods that are nutrient-poor and don't support your health or recovery, you're not doing your health any favours.    

It is important to choose nutrient-dense, unprocessed, and wholesome foods in the right quantities. This will improve your recovery and ultimately your body's health and fitness. 

Not drinking enough water 

Drinking sufficient water is often neglected. To replace fluids that are lost, ensure that you drink a combination of water and electrolytes.

Here's a practical tip: check your urine after an exercise session to ensure that you are properly hydrated. Aim for a light colour as soon as possible after your session. The guideline is that you should be drinking 250ml of water for every 10kg of body weight, and extra when you are exercising and losing a lot of fluid through perspiration.

On a final note, remember that although all the above guidelines need to be considered, they are, however, only guidelines and recommendations, and not fixed rules.

The best approach would be to consult a dietitian, who will be able to assist you with formulating a healthy, balanced eating plan and menu taking your individual and specific health, lifestyle, and training goals into consideration. They will also be able to assess if you need to use supplements. Be cautious of the advice and recommendations you read and listen to. 

Let our team of registered dietitians at Nutritional Solutions help you "make healthy happen". We offer expert nutritional advice based on evidence-based practices. Go to for more information. 

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