I was reading in the media today how athletes in some sports cut weight rapidly to reach a target weight for pre-competition weigh ins.  Some will lose between 5-10% of their body weight in the days before a competition which has resulted in deaths!

To me – someone not competing in those competitive weight-based sports – it seems crazy.  Five to ten percent of an average healthy woman’s body weight of 60kg is equal to 3-6kg.  It doesn’t sound much but for anyone who has tried to lose weight we know it takes time to lose that amount.  The recommended rate of weight loss is 0.5 to 1kg per week.

Mind you, we are comparing apples with oranges here.

The athlete is losing mostly fluid, that’s right, water; this is done by dehydrating the body – including drinking no fluids and sweating in heavy clothing and saunas.  Whereas the average woman is more interested in losing fat – or that bit that oozes over her waistband or bulges round her bra straps, to be exact!  And no, we can’t pick where we lose the fat!

So what happens when you go on a ‘diet’ to lose weight? 

Some restricted energy (when I say energy, think kilojoules or calories) diets make you lose weight really quickly at first while others don’t.

Some weight loss diets will have a week or more of a very restricted phase then will move to a second phase which is less restrictive and where you lose weight more slowly.  What is the difference between these phases and what is actually happening in the body?

Phase 1

Usually, the eating plan in phase 1 is low in carbs (carbohydrates) so your body uses its stores of glycogen, a storage form of glucose found in the liver and large muscles.  For every gram of glycogen there are 3-4 grams of water stored with it.  So for every kilogram of glycogen used you lose an additional 3-4kg of weight from the scales! A-m-a-z-i-n-g! Right?  Well, not really. 

The body will try to replenish this store of glycogen next time you eat enough carb containing food and until then you feel really tired. But – and this is a big but – the loss on the scales can make you very motivated to keep going.

The first phase of a structured weight loss plan can give you motivation to keep going!

Phase 2

The next phase of the weight loss diet will have more carb, so you feel less exhausted, but you won’t have the continued rapid weight loss.  If there is a lesser amount of energy going into your body and more being burned by exercise and normal day to day functioning and activities, then you will continue to slowly lose weight.  Most of this weight loss will be from fat and muscle.

Muscle!?  I hear you shriek – not that muscle that I work so hard to build at the gym?  Yes, unfortunately, we will break down both fat and muscle.  Our bodies will break down fat stores into fatty acids and muscles into amino acids to burn for energy as we lose weight.

The trick is to keep up your resistance exercise while you are restricting your eating, so you maintain as much muscle as possible.

Okay, for a quick refresher on what resistance exercise includes.  Think:

  • free weights and other heavy objects like kettle bells, medicine balls or even cans from the pantry
  • weight machines
  • resistance bands (those big rubbery bands or tubes)
  • body weight exercises including yoga and pilates.

Australia’s Physical Activity and Sedentary Behaviour Guidelines for Adults recommends we do 2 sessions every week of resistance exercise.  My recommendation is to be guided by a PT or exercise physiologist about what you do and try to space it out over the week to give your body time to recover or have at least a whole day between resistance sessions.

In the meantime, keep up your energy restricted diet and check the scales or your measurements regularly to see how you are going.  Don’t get too stressed if the number on the scale isn’t changing too much, your measurements or even checking how your clothing is fitting provides better information for your progress – before and after photos are valuable here.  After all, if you are gaining muscle with your exercise and losing fat (and some muscle) with the energy restriction you could weigh more but be smaller.  It’s one of those healthy lifestyle anomalies.

So, to summarize:
  • Extremely rapid weight loss is bad for your health and can result in death – avoid it.
  • The recommended rate of weight loss is 0.5-1kg per week .
  • Carb restriction can result in temporary weight loss from using up glycogen stores and losing water – as part of an initial phase in an energy restricted diet it can give you motivation to continue.
  • Weight loss will occur as you restrict your energy intake and increase your energy output – think less food and more exercise.
  • Maintain your muscles by doing 2 or more sessions of resistance exercise each week.
  • Be guided by your dietitian and PT or exercise physiologist.

Anyway, I’m off to the gym… have a good week!


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Post byDale Cooke

I'm a nutritionist, dietitian and personal trainer with 29 years of experience helping people improve their health. I really like using a non-diet philosophy to achieving a healthy lifestyle. Can I help you improve your health?