I have a few comments on the discussion about swimming, running, _meta_bolism, and fat.  My newsreader is 10 days behind, so I don't know what's been posted in the last week or so.   ENERGY BALANCE Let's not loose sight of the fact that whether you are swimming, running, rowing or chopping wood, the bottom line is that if you expend more energy   than you consume over the long term, your body will have to burn fat to make up the energy deficit. So regardless of which activity burned more fat or glycogen during a workout, all physical activities will allow you to lose fat if you expend more energy than you consume over the long term.   If an athlete has a 2000 calorie _base_ _meta_bolism energy requirement and   expends an additional 2000 calories during workout, then he/she must consume 4,000 calories per day to maintain the same body composition.  Consume less than 4,000 calories and fat will be burned to make up the difference, more than 4,000 calories and fat weight will be gained.  (simple model, not considering the possibilities of rapid muscle gain, or muscle loss) APPETITE Therefore, those who suggest that swimmers will have difficulty losing weight or maintaining a lean physique while runners will be inherently lean are heavily dependent on the energy intake side of the equation.  Clearly enough calories to lose weight can be expended by both running and swimming. I have read testimonials in SWIM Magazine and r.s.s from people who feel more hungry after a swim workout than after other athletic activities.  For these people, swimming definitely presents an additional difficulty if they are trying to lose weight.  If these people cannot control their appetite after swimming, then they probably should consider another activity to lose weight.   I would like to point out that not all people feel this way.  I, for one. I went through high school swimming double workouts several times a week. During this time I ate a bowl of cereal and two pieces of toast before morning workout, swam for an hour and fifteen minutes, went straight to school, and didn't eat or consume any beverage but water until lunch at noon.  Never suffered from any major hunger pains, never had any energy problems.  Also, after graduating college I got into triathlon,  Did a lot of biking and a lot of running.  Never noticed any difference in my appetite after biking or running compared with swimming.  I am not alone in this respect.  Throughout all my years of swimming and triathlon I have trained with people who had no trouble with excessive appetite after swimming.   FAT RUNNERS Anyone who runs and participates in local running races knows that most runners are not exceptionally lean.  In fact, my personal observations suggest that most runners at a local running race are not lean at all.   Many times I have been surprised by the flabby stomachs on runners who are quite fast. At both my previous and present jobs there are a lot of lunch time runners.   The huge majority of them do long easy runs almost every day.  This is just the sort of activity that fat burning runner theorists believe should be burning fat with great efficiency.  Yet, I can think of only one or two of these people who were genuinely lean.  Most of them are in decent shape compared with the general population, but not lean.  Many of them are diet conscious, yogurt and power bar eating types to boot.   I have also known many Clydesdale (very heavy) runners, who ran 40 to 50 miles per week, long slow distance, and never became lean.  I am interested to hear what fat burning runner theorists have to say about the above observations.  At a minimum I think it is safe to say that the fat burning magic of running (assuming there is anything special there at all), has major limitations.  One need only take a look around to see that.   Yes, elite runners are usually very lean.  But, so are elite swimmers.   LEAN SWIMMERS Swimmers who work out seriously are almost universally lean.  Through years of USS club swimming and college swimming, I can think of few exceptions.  Many recreational swimmers are not lean.  But, most recreational runners are not lean either.  Elite swimmers are lean.  Many of us watch USS championships, NCAA championships, Pan Pacs, Olympics, etc. on T.V. Anyone care to point out some elite swimmers who are not lean? I will acknowledge that elite swimmers might have a percentage or two more body fat than runners.  But why?  I believe it is because an extra pound of fat is much more detrimental to an elite runners performance than it is to an elite swimmer.  In swimming the extra weight is mitigated by water's buoyancy.  An extra pound of fat is primarily detrimental to a swimmer only due to the extra drag which might be caused by a slightly greater cross-sectional area (i.e., very little extra drag).   LEGS Runners derive most of their propulsion for big leg muscles.  Swimmers derive most of their propulsion from smaller muscles: lats, shoulders, tris, back, etc.  However, swimmers USE their leg muscles a lot!  Fly has a powerful kick that is essential to do the stroke well.  Breaststroke has a very powerful kick.  Backstroke too (must be the reason my legs hurt so much when I swim backstroke).  Only distance free_style_ can be done well with a light kick.  And, what about those major pushes off the wall every 15 to 18 seconds or so (in a 25 yard/meter pool)?   I maintain that competitive swimmers who train seriously use their leg muscles extensively.  Why wouldn't the powerful use of legs in swimming burn fat just as it does in running?   Common sense and many points of personal reference suggest to me that people should not jump to the conclusion that they cannot maintain a lean physique, or cannot lose fat through swimming.....  UNLESS you feel that swimming causes you to over-eat.   Interested to hear any comments, please email me, have a good day, ed