exercise duration for fat-burning

[Jorge]

Hi
There's been some info online recently about testing the common & long held belief that when exercising to burn fat, the exercise duration should be over 20 minutes, as this is the time it takes for the body to start burning fat calories. Its what I learned when younger, & personally what I've always believed & practiced, but would be interested to hear some thoughts on this from you fitness junkies.
Regards
jsierra

[katia]

dunno.  the one thing you can be sure of is that when you are exercising you are almost always burning up fat, all that differs is the rate at which you are burning it up.  my opinion is  that a moderate exercise routine is the best.

[Gill]

Hi there:

my experience with this is as follows; I think the recommended amount of time for exercising is 20-30 mins per day.  It doesn't matter if you do this all at one time or break it up in 10 mins intervals.  So walk around the office, climb some stairs, desk push ups (lean over, hands on desk and do push ups - strength training), it all counts and all are fat burning.  That's what I've been taught through the University.  The best fat burners are the strength training ones that actually increase muscle and decrease fat.  Aerobic types are for the heart.  A combination of both is the right mix.

Gill

[Jorge]

All sounds interesting so far.  One consideration in all of this though, is that the body is said to burn up carbohydrate calories during the first twenty minutes of exercise.  So it appears there are varying beliefs on the issue of exercise duration in the fitness/nutrition field.
As for strength training, it is questionable if it contributes to fat-burning, as it is anaerobic, & performed in short bursts of highly intensive energy, with rest intervals in between. Which makes sense, as exercises should be performed to failure, where no more repetions are possible, so that strength is gained through replenishing. Fat-burning on the other hand would require aerobic exercise, where it is moderate & continuous.

some other considerations brought to my attention lately are that the body is more likely to rely on fat calories for energy when:
exercising prior to the day's first meal;
& exercising 2-3 hours after a meal (whereas when exercising one hour after a meal, the body is likely to utilise more carbohydrate calories for energy).

[Gill]

It's a science to be sure, with all little knooks and crannies.

Gill

[bodyfattest]

Here is the deal.  If you are going to work out for 20min or more (strenuously) make sure you eat a light snack within 60 mins before and after.  Otherwise you will loose lean mass over time.  Also look at your diet and excersise over a weeks period.  It doesn't matter how much you work out you will be fat if you eat too much.  There are 3500 calories in a pound of fat and if you eat 3500 less or workoff 3500 more then you will loose a pound. It is that simple. The pound you lose will be muscle, fat or combination of the two, depending on what and when you eat. 
FAQs: You should have protein and carbs.  A light snack is only about 50-100 calories. Eat 5 or 6 small meals per day. 

[BrandiOK]

  Strength training isn't the primary fat-burner it's the resulting muscle tissue that is.  The more muscle you have the more calories your body is burning to maintain that muscle whether it be at work or at rest.  That's not to say that you have to pack on huge amounts of muscle mass to garner the benefits just build a "healthy" muscle framework for your body size.  Using strength training to tone existing muscle tissue has the same effect, although not to the same degree obviously, as building muscle mass.

  The reason they suggest to exercising for 20 minutes it ensures that your heart rate is not only elevated but stays elevated for a sustained time.  The heart is a muscle and since we can't give it a set of dumbells to work out with we do it by making it work harder. In other words the 20 minute time is to work out your heart muscle effectively......while exercising for burning additional calories isn't confined to a certain time. 

  Carbohydrates are the first thing burned by the body for fuel.  The pitfall is that most people consume many more carbohydrates than thier body can process.  Any carbs you eat that are not burned become sugars and are then added to your bodys fat stores.  Considering the HUGE amount of carbs most people consume it's almost impossible to burn them off with exercise.  Hence the reason "carb loading" or purposely consuming large amounts of carbs should be done only by those atheletes who train enough to burn them. 

  If you want to lose weight you decrease the amount of calories you take in and increase the amount of exercise you perform.  Once you begin to burn more than you consume you will lose wieght.  As mentioned your body needs both protiens and carbs as well as healthy unsaturated fats but the proportion needs to be a healthy one. 

  I think we get confused because we are flooded with all kinds of false information by food manufacturers, pharmaceutical companies, diet makers and even our own government.  The best thing you could possibly do is talk to a fitness nutritionist....these people are the ones who know what works and why.