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Question
Posted by: Lara | 2012/07/16

curious about metabolism

Dear Dietdoc,

When people say skipping breakfast lowers your metabolism or puts your body in " starvation mode" , what exactly is the mechanism that sends this signal to lower (or speed up) the metabolism? Is it the blood sugar level? Is there a minimum number of calories one has to have to kick-start this process?

Also, if a person who hasn''t eaten breakfast for many years starts doing so, how quickly would it have an effect on her metabolism?

Thank you!

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Our expert says:
Expert ImageDietDoc

Dear Lara
The mechanism by which the human body recognises that it is being 'starved' is very complex and consists of a variety of signals generated by changes in blood sugar levels, changes in your basic metabolic rate, changes in the stomach and intestines caused by lack of food, changes in levels of signalling hormones such as leptin, insulin, glucagon, etc. The human body is always geared to trying to maintain a perfect balance, so if you disturb one factor (lack of food input), then all the other systems in the body will try to compensate for this by switching on or off. In the case of reduced food intake, the body will compensate by conserving energy. Consequently most people achieve more consistent weightloss by using a diet with a moderately reduced energy content and by increasing their physical exercise. The latter can increase the basic metabolic rate which uses up a lot of energy for up to 24 hours, thus promoting weightloss. In general it is recommended that adult women ingest about 1500 kcal (6300 kJ) per day when trying to lose weight. How quickly eating breakfast would affect metabolism depends on the individual, but in most cases the effect would be quite rapid because the person in question would no longer be suffering from extended periods of low blood sugar (i.e. if the last meal was eaten at 7 pm the night before and the next meal is only at lunchtime, this represents a starvation period of up to 17 hours).
Best regards
DietDoc

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1
Our users say:
Posted by: DietDoc | 2012/07/17

Dear Lara
The mechanism by which the human body recognises that it is being 'starved' is very complex and consists of a variety of signals generated by changes in blood sugar levels, changes in your basic metabolic rate, changes in the stomach and intestines caused by lack of food, changes in levels of signalling hormones such as leptin, insulin, glucagon, etc. The human body is always geared to trying to maintain a perfect balance, so if you disturb one factor (lack of food input), then all the other systems in the body will try to compensate for this by switching on or off. In the case of reduced food intake, the body will compensate by conserving energy. Consequently most people achieve more consistent weightloss by using a diet with a moderately reduced energy content and by increasing their physical exercise. The latter can increase the basic metabolic rate which uses up a lot of energy for up to 24 hours, thus promoting weightloss. In general it is recommended that adult women ingest about 1500 kcal (6300 kJ) per day when trying to lose weight. How quickly eating breakfast would affect metabolism depends on the individual, but in most cases the effect would be quite rapid because the person in question would no longer be suffering from extended periods of low blood sugar (i.e. if the last meal was eaten at 7 pm the night before and the next meal is only at lunchtime, this represents a starvation period of up to 17 hours).
Best regards
DietDoc

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