From every mouth who has some knowledge of training says that swimming is the only exercise which uses lots of major muscles of our body, swimming is an incredible way to burn fat, but people tends to store fat due to swimming.
I was also among those people who stored body fat due to swimming, when I started swimming I body fat percentage was 11 % and my goals is to drop it down to 9% but after 1 month of swimming I gained 1 % additional body fat. I was so anxious to know why this happen to me as I am taking care of my calories intake and all physical calories expenditure but some how I missed these three main reasons which are responsible for my fat gain due to swimming lets discuss it one by one.
1. CORE BODY TEMPERATURE.
When we do swimming it reduces our core body temperature, even hard swimming in relatively warm water reduces the core body temperature, the core body temperature plays a major factor in our hunger and satiety. Core body temperature is an operating temperature for our vital organs. It is a physical state in which our internal vital organ and body systems work efficiently. The human body has to maintain core body temperature in order for the optimal functioning of the vital organ.
The ideal core body temperature of a human is 37.7 °C, it is also called a normothermic state. core body temperature can vary from person to person because every person has individual physiological factors i.e Muscle mass, fat mass, Basal metabolic rate, Age, etc. The human body has been designed to operate optimally within the range of 36°C to 39°C. When our core body temperature approaches the lower range 36°C or below it(it is also called hypothermic state), our body gets in alert mode, it tries to take corrective majors to bring back the core body temperature within the optimal range. The hypothalamus part of our brain start the vital organs saving mode by reducing the volume of blood circulating near the surface of the body in order to retain a greater volume of warm blood near the internal organs. In similar fashion when our core body temperature approaches the upper limit (40°C) or above it, our brains just reverse the action by increasing the blood volume near the surface of the skin to promote a cooling effect & it also instructs to sweat glands to release sweat in order to cool down the body. Thus by this inbuilt mechanism human body controls their core body temperature.
Secondly, as we well know that our stored body fat serves basic three functions in our body which are:
a) Energy reserve.
b) Protection of vital organs from sudden high impact jerks.
c). Insulation, it insulates our body and helps our body to sustain a normal core body temperature.
So as per above third point (c), our body uses fat for bringing the core body temperature within its normal optimal range. thus whenever our core body temperature gets low body start accumulating more fats, human body stimulates more fat storage when core body temperature falls down, the body's fat storage ability starts increasing whenever your body has undergone a low core body temperature.
When these two phenomena hunger & body's fat accumulation ability stimulate together you tend to eat extra calories to satisfies your appetite thus these extra calories get stored as body fat after swimming which is difficult to get rid of. Also, people overestimate the calories burnt while swimming, swimming makes us more tired but the actual energy cost of swimming is low, thus people overestimate it that they have burnt more calories and then to maintain the calorie balance they consume more calories, these extra calories go directly to body fat reserves making your body fat percentage to increase its reading.
You may also have observed the phenomena of core body temperature during sessions, as winter comes you tend to consume more food while you reduce the calorie intake in summers as it is due to a chemical reaction which is going inside our body while adjusting core body temperature in reference to atmospheric temperature.
Although swimming is a low impact exercise, it takes more physical efforts, you can run 100 m easily but you have to struggle to swim 100m in that time frame, the world record of running 100m is of 9.58 seconds set by Usain bolt while the world record of swimming 100m freestyle is 47.05 seconds set by Eamon Sullivan, thus you can see the difference it take approx 5 times more to cover the same distance by swimming than running because of the resistance water.
The type of exercise you choose to swim determine your intensity as doing freestyle, dog peddling is low intensity while swimming with butterfly stroke, breast stroke requires great efforts. Thus when you apply more physical efforts our body energy providing mechanism sifted to anaerobic from aerobic, and we well know the fact that our body burns fat in aerobic activity and it burns glycogen/sugar in anaerobic to supply the energy demand of exercise.
If you are beginner you have to put lots of effort to swim while an advanced swimmer can swim easily thus he/she burns fat while due to applying more efforts a beginner burns glycogen/ sugar. I also join swimming to burn fat but as I was the beginners I had to place lots of efforts to swim thus my body burns more glycogen to provide the energy for swimming instead of stored fats. People always tends to ignore this point and gain body fat while in start of there swimming sessions.