Originally Posted by r2473
I would say that tennis is unlikely to be the total (or best) solution, but I would challenge you to find a single reputable person that recommends a fat loss plan and no exercise.
Of course, almost every reputable person recommends it because it's physiologically irrefutable. Unfortunately, as the vast numbers of obese and overweight people in the Western world who know that diet and exercise are "the key" to losing weight will testify, the physiological theory isn't the issue, the psychological practice is.
Incidentally, you say "fat loss plan"; there are lots of reasons why focusing on the consumption of fat (if that's what you're suggesting) won't work. Many low fat foods have another ingredient that increases calories directly or indirectly. Fat per se isn't an issue; the calorific density of fat may be, but even that's beside the point.
The problem with focusing on exercise to lose weight is that studies show that people routinely over-estimate the calorific impact of exercise and feel they can reward themselves with foods.
The original poster is doing a smart thing to try and get a reliable estimate of the calories consumed in exercise, but it will be impossible to give an accurate guide because none of us can be sure how efficiently he plays; only scientific measurement of the individual could provide this. However, the issue of weight loss isn't a conscious one. If it was everyone who was told that to lose weight you need to exercise more and eat less and who decided they wanted to be slimmer would achieve their desired outcome. The unconscious mind has a mental age of approximately six years, and takes many, many months to change. Unfortunately the unconscious drives the vast majority of our behaviour.
I recommend that the original poster reads The No Diet Diet. It's not a weight loss panacea, but at least it puts the emphasis in the right place - the preoccupations of the unconscious mind.
And another thing; diet sodas. Another grand weight loss illusion. Whether the artificial sweetners trigger hunger sooner, or whether people unconsciously miscalculate the punitive benefits and then over-indulge elsewhere isn't clear, but a large long term study found that when of the two groups it was the diet soda drinkers that ended up with higher proportions obesity.
Of course, if you take your sugary Gatorade to the court when you go to play tennis to "lose weight" there's a pretty good chance you'll negate calorifies burned before you've left the court!