Training & Nutrition - Am I gonna get a big butt from riding? While I loose the tire area?

Looking at general physical condition I would say I am in quite decent shape, and I always do well in endurance competitions (x-country skiing, running etc). I am 26 years old, 5 feet 7 inches, roughly 140 pounds and skinny looking. The past 8 years or so I have had 3 years of pretty intense training, one year of absolutely no training, and the last 4 I have been working out on a regular basis. My weight has never changed more than a couple of pounds back and forth. (I would just like to point out that my year of no training was horrible, I will never do that again. I am restless and enjoy working out)

First issue:
I have a small "tire" area, one that I have had at least since high-school (I can see my stomach muscles well when looking in the mirror, but looking at it from a profile it is down there, pointing maybe a little less than an inch out). I eat reasonably healthy with little fast food on the menu. That said, I don’t really have a diet of any kind and if there are sweets on the table I eat them! Looking at how constant this layer of fat has been through highly varying training intensity it looks like I am stuck with this. Is that just something I will have to accept unless I quit my job to work out all day?

Second issue:
I was born with a big butt. Not wide, not flabby, it just points out back there! I have only been riding for a little over a month so I am not an experienced cyclist. Will my butt get smaller (trimming off fat), or bigger (more muscles adding to the volume, hehe)?

I can speak to the tire issue: A lot of men are genetically predisposed to having the spare tire (no matter how small it may be).

I know that in my days running cross country my milage would reach as high as 70 miles per week (113 km), and I would be otherwise very thin to the point of appearing gaunt-- but the tire would never go away. I suppose I could have done more milage in order to have lost that annoying ring, but having done so would have been at the expense of real strength (70 miles per week was really my practical limit).

Cycling might be different, however, as it's a low impact aerobic exercise-- and perhaps such work-load limitations don't exist in the same way. I'm just figuring this out as it's my first year of serious cycling.

Women, on the other hand tend to be genetically predisposed towards having more fat around the butt. I've never met a woman that seemed too comfortable with this fact, but that's the reality of the matter. It's what makes women look like women, and in my opinion, it looks good. Cycling won't add fat (that's a no brainer) but it could very well add definition. Not a bad thing at all, methinks.

The spare tire holds the unhealthiest kind of fat. Known as visceral or abdominal fat, it is a strong risk factor for diabetes and coronary artery disease. It really pays to get ride of it! Butt fat is not so much a health issue, although it may affect your appearance.

Unfortunately, for most men, and many women, abdominal fat is the hardest fat to lose. Like many others, I can lose weight until I am really gaunt all over my body, and still have a pot belly. You might want to add some weight lifting and even more cycling to increase muscle mass and speed up fat loss, without looking too gaunt. Of course, if you are going to be racing, you might prefer to just be skinny, and skip most of the weight work.

Many cyclists say they see more increase in size of the quadriceps (front of thigh) rather than gluteus.