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Disadvantages of too little calorie intake – harmful effects on the body.

Many people find it hard to believe that under eating can often cause as many health problems as over-eating! Eating too little can cause negative effects on training performance, exercise goals and also long-term health and well being.

What are calories and why are they important for exercise?

Calories are a measure of energy and are used to describe how much energy content is within the food we eat. We need energy to exercises because if we don’t exercise our muscles and bones can become weak.

It is hard to highlight an ideal calorie intake every woman should abide by because everybody’s body composition and activity levels are different. However, the general guide from the NHS is women should consume 2,000kcal/ 8,400kJ a day. Slight decreases in calorie intake e.g. 300 per day can be helpful in weight loss but larger decreases can promote changes within the body to maintain homoeostasis which can have unwanted effects on the body and exercise performance.

The effects of eating too little calories can be divided into short term and long term side effects.Personal trainingShort term effects

If you fail to consume enough calories in relation to the physical activity you perform you can cause a number of short-term side effects. The first symptoms you may notice include feelings of weakness and dizziness.You may also feel sluggish, irritable. This is because when you workout without eating your body seeks energy in the stored glycogen and blood glucose. However, these stores can become depleted very quickly causing hypoglycemia (low blood sugar). As the brain is fueled by glucose when levels of glucose drop this can explain why you feel symptoms such as dizziness and weakness. Exercising without adequate calorie intake can also lead to an increase in the release of cortisol. Cortisol is a stress-related hormone that can leave you feeling, stressed, irritable and anxious.

Overall, if you do not consume enough calories your workouts could be unsuccessful and not enjoyable!!!!

Long term effects

In addition to the short-term effects of inadequate calorie intake detailed above. Poor diet for a prolonged period of time can have long-term effects on your health. Malnutrition can lead your immune system to become less effective meaning you are more susceptible to the common cold and flu and you may even become anaemic. Prolonged low-calorie intake can also lead to hypothalamic amenorrhea, this is when menstruation stops for several months because the hypothalamus gland within the brain slows or stops the release of gonadotropin-releasing hormone (GnRH) (the hormone that initiates the menstrual cycle). If amenorrhea continues for a prolonged period of time it has been found in some cases to lead to infertility. Furthermore, due to a reduction in the production of oestrogen experienced during amenorrhea, it could lead to an increased risk of osteoporosis or osteopenia (weak bones).

Overall, prolonged states of low-calorie intake with exercise can lead to various health complications including a weakened immune system, hypothalamic amenorrhea, osteoporosis and osteopenia.Fierce Fit patient using exercise ball to aid in exerciseThe benefits of a healthy diet when exercising:

Maintaining a healthy and balanced diet throughout a training programme can produce many benefits. Such benefits can include both physical and psychological components such as;

  • High energy levels
  • Feel alerted and motivated
  • Ability to concentrate
  • Feel strong and capable
  • Decreased onset of fatigue
  • Improved recovery rate
  • Reduced risk of injury
  • Reduced risk of osteoporosis/osteopenia
  • Healthy immune system

If you have any questions about what to eat or when to eat our team of personal trainers are more than happy to help!

author: Louise Rigby

Louise Rigby graduated with a Sports Therapy (BSc) Hons degree in 2015 from the University of Central Lancashire. Alongside her degree she has attained a VTCT level 4 certificate in sports massage therapy and holds a Level 2 emergency aid and trauma management qualification. She is a member of the Society of Sports therapy and takes part in regular CPD. Through her time at university Louise gained experience in the assessment, prevention and rehabilitation of musculoskeletal injuries and has worked with sports teams such as the Rochdale hornets and the Fijian rugby league team. Louise has always had a keen interest in sport and exercise and has performed competitively in gymnastics, cheerleading, dancing and volleyball. In her spare time Louise enjoys going to the gym and socialising with friends. She is a passionate and enthusiastic individual which can be observed when meeting and treating her massage patients!


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