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4 Sports Nutrition Mistakes You Could Be Making

July 14, 2021


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Whether you exercise regularly or are an amateur or a professional athlete, getting the right balance between exercise, recovery and nutrition is fundamental in preventing injury and being able to perform at your best.

We take a look at the top 4 common mistakes people make when it comes to sports nutrition, and how this may be affecting your health and ability to exercise well.

Top 4 Sport and Exercise Nutrition Mistakes

Proper nutrition and hydration are vital for sports performance, even if you just exercise a couple of times a week. Many people underestimate the amount of food or drink they need to keep themselves going.

Simply put, you can’t drive a car without fuel and the same is true for your body. The problem is, you may not realise you’re doing anything wrong, even though the signs and symptoms may be apparent.

Here are our top 4 sports and exercise mistakes:

 1. Not Eating Before Exercise

If you are the type of person who wakes up and dashes straight out for a run or early morning gym session without any substantial food beforehand, you are putting undue stress on your body.

This is because you have been without food or water for around 8 hours while you sleep, essentially fasting throughout the night.

Not having enough fuel to support the level of exercise you are doing means the body has to find energy from other sources.

The most immediate source of energy for the body are carbohydrates which are stored as glycogen in our muscles. The next source is fatty acids. In extreme circumstances where there is chronic under-fuelling of the body, it will turn to breaking down muscles once it’s exhausted glycogen and fatty acids [1].

Continually exercising without eating enough to fuel the body can result in the body storing more fat to use as energy – so counterproductive if you are trying to lose weight.

In addition, exercising on an empty stomach and without adequate hydration will make you feel weak, lightheaded, and dizzy due to low blood sugar levels and dehydration.

Runners on treadmill

2. Cutting Out Carbohydrates

Diets that reduce or cut out carbohydrates is not recommended if you are doing a lot of exercise. Because carbohydrates are the main source of energy for the body, reducing the intake of carbohydrates means your body doesn’t have sufficient sources of energy and make resort to fatty acids instead to get the energy it needs to perform.

Even on a small scale, a lack of carbohydrates in the diet can lead to fatigue, reduced energy during exercise, and increased recovery times [2]. The longer you exercise and the harder your body works, the more carbs it needs to keep up with the demand.

How much carbohydrate you need in your diet depends on the level and intensity of exercise you do. High-intensity exercise requires more carbohydrates as the body uses a higher proportion of carbohydrates to fatty acids [1], whereas low-intensity exercise uses a higher proportion of fatty acids for energy, so you need fewer carbohydrates.

3. High Protein Intake

Protein is important for sports performance as it helps muscles to recover from exercise and reducing muscle soreness post-workout.

According to the British Nutrition Foundation, while a diet high in protein can be beneficial for athletes and those regularly participating in sport and exercise, it should be part of a balanced diet.

A high protein diet without sufficient levels of carbohydrates to match the intensity of exercise you are doing will deplete the body of a valuable source of energy. In addition, protein alone will not help build muscle mass [3].

Man drinking protein shake after working out

4. Not Eating Enough

For some people, exercise is combined with dieting to help with weight loss. But not consuming enough food to support the energy needs of your body can have a detrimental effect on your health.

As we’ve touched on in point 1, your body needs energy in order to perform and this energy comes from food both in the forms of carbohydrates and protein.  You should be consuming enough food throughout the day to fuel your body to carry out not only the exercise you are doing but the day-to-day tasks as well.

If you exercise along with cycling to work, doing housework, playing with the kids and taking the dog for a walk – all this is using up energy, so the amount of food you eat needs to be able to fuel all of these activities.

Not eating enough or not eating the right types of foods your body needs to meet the physical demands you place on it is known as under-fuelling. Ultimately, under-fuelling undermines or even reverses the hard work you’ve put in to reach your exercise goals.

How Does Poor Nutrition Affect Exercise?

Poor nutrition is a major cause of under-fuelling in sports performance and exercise that leads to a wide range of issues both physically and mentally.

Chronic under-fuelling can lead to what is called Relative Energy Deficiency in Sport or RED-S. The condition is defined by the International Olympic Committee as “impaired physiological functioning caused by relative energy deficiency and includes but is not limited to, impairments of metabolic rate, menstrual function, bone health, immunity, protein synthesis, and cardiovascular health.” [4]

It’s caused by restricted eating and overtraining [5]. When there is low energy availability due to insufficient nutritional intake, the body is unable to meet the physical demands placed upon it [6].

Performance Dietitian, Renee McGregor, puts it like this:

“… there are a lot of athletes who will focus on the energy they need for their training. But don’t take into consideration other energy needs, such as the biological processes that go on inside the body every day, or the energy needed for those who are commuting by bike, have an active job or a young family. It’s quite hard sometimes to appreciate how much energy you need!”

However, this isn’t something just top-performing athletes can suffer. If you regularly exercise and do not eat enough food to support your energy output, then you will begin to notice the signs of under-fuelling.

What Are The Signs Of Under-fuelling?

There are several signs that indicate you may be under-fuelling; the initial signs may not be as serious as the long-term risks.

Signs of under-fuelling, include:

  • low energy
  • fatigue
  • disrupted sleep
  • irritability
  • muscle loss
  • bone density loss leading to osteoporosis
  • difficulty concentrating
  • becoming more prone to illness
  • irregular or lack of periods in women (known as amenorrhoea)
  • stress injuries
  • slow recovery times
  • decrease in performance [4].

In addition, not giving your body enough fuel to function can also lead to hormone imbalance as the body priorities other core functions – essentially going into survival mode.

This is particularly notable in women as they will notice changes to their periods or will have missed periods. In extreme cases of under-fuelling women’s periods may stop altogether. If this continues for at least 3 months, then it is known as amenorrhoea.

The chart below shows how important it is to get the balance right between exercise, nutrition and also recovery (rest days) to ensure your hormones stay healthy.

Harnessing hormones through behaviour

Learn more about the role of hormones in women’s health>>

If you want to gain deeper insights into how your exercise routine may be impacting your hormones, then our Female Hormone Mapping product can help. It maps out all 4 key female hormones across your entire menstrual cycle using a combination of artificial intelligence and blood analysis. You can learn more by reading our blog ‘What Is Female Hormone Mapping?’.

Although most of the research into RED-S involves women, there is emerging evidence that shows men are affected, too. It seems that there is a greater risk in males who participate in sports such as cycling, rowing, combat sports, distance running as well as jockeys [8].

However, it is likely that there are different biological consequences in male athletes compared to female, but a major concern is thought to be a reduction in testosterone [4, 7].

What is Good Nutrition for Sport & Exercise?

Eating a balanced diet that includes carbohydrates, protein, a good mix of fresh fruit and vegetables, whole grains, and unsaturated fats, will help to keep your body fuelled and reduce the risk of nutrient deficiencies.

You should eat a meal 2-3 hours before a workout or training that contains the right amount of carbohydrates and protein in order to provide your body and muscles with energy and strength. 

If you are unable to eat a complete meal 2-3 hours prior to exercise, then it’s a good idea to have a light snack an hour before. 

A light high carb, moderate protein and low-fat snack is ideal as this can help to boost your energy and aid your recovery afterwards.

Choose an easily digestible snack like:

  • porridge with banana
  • a slice of wholegrain bread with a thin layer of peanut or almond butter
  • yoghurt with red berries
  • cottage cheese and oatcakes or crackers

Post work out, your focus is on restoring your energy levels and aiding muscle repair and recovery. Therefore, you should consume the right amount of carbohydrates, proteins, and nutrients to help repair muscles and build up your stores of glycogen.

Endurance sports such as running or cycle will require higher carbohydrates and moderate protein, whereas strength training will require higher protein and moderate carbohydrates.


Under-fuelling has a detrimental impact on your sports performance as well as overall health. There are long-term risks associated with under-fuelling including RED-S which can have a profound impact upon many of the body’s systems.

For you to meet your exercise goals and ensure you do not put unnecessary stress on your body you need to be eating the right foods at the right time.

The most important aspects are energy-in in the form of carbohydrates to support the level of energy out in the form of exercise and day to day living. Plus, eating the right amount of protein based on the type of exercise you are doing to help aid muscle strength and repair.

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Article references

  1. Mountjoy, M et al. (2018). IOC Consensus Statement on Relative Energy Deficiency in Sport (RED-S): 2018 Update. British Journal of Sports Medicine: 52(11).

  2. Tenforde, A, S et al. (2015). Parallels with the Female Athlete Triad in Male Athletes. Sports Med.

  3. Burker, L, M et al. (2018). Relative Energy Deficiency in Sport in Male Athletes: A Commentary on Its Presentation Among Selected Groups of Male Athletes. Int J Sport Nutr Exerc Metab: 28(4), pp 364-374.

This information has been medically written by Dr Thom Phillips

Thom works in NHS general practice and has a decade of experience working in both male and female elite sport. He has a background in exercise physiology and has published research into fatigue biomarkers.

Dr Thom Phillips

Dr Thom Phillips

Head of Clinical Services