Is it true that Increase in HDL causes decrease in HDL? Does HDL Physically decrease LDL..If so,how?

The question is:Does HDL actually 'eat away' LDL and not allow LDL to stick to blood vessels??

re-write the question, it doesnt really make sense, do you mean high HDL lowers LDL?

Your question isn't clear. Are you asking if raising HDL lowers LDL?

BTW, ignore Razwell. He's got a one track mind.

HDL is "good cholesterol" I remember this as the "H" stands for happy.
LDL is "bad cholesterol" or loser.
HDL does help decrease LDL, but I can't remember how.

That there is a 'good' cholesterol and a 'bad' one is medical myth.

There is a lot of evidence that the lipid hypothesis is a grand failure.

There are many scientists who thoroughly question this hypothesis, not least because humans have been eating animals and animal products FAR longer than so-called 'low cholesterol' things like vegetable oils.

You should do a google search for 'cholesterol myth'. Listed below are some. For instance, the body produces far more cholesterol in a day than you can eat by a large margin. To assume that what small amount you're going to eat will have a dramatic effect on the total is silly.

There's also evidence that having too low a cholesterol will increase your chances of dying from many illness (called 'all-cause mortality').

Some of the more prominent sites containing this scientific information are:

The Cholesterol Myths [1]
The International Network of Cholesterol Skeptics [2]
Fats, cholesterol and cardiovascular disease index [3]
Cholesterol and Heart Disease--A Phony Issue [4]
The Benefits of High Cholesterol [5]

You will also notice that in conjunction with this topic you'll run into information that exonerates saturated fat as this evil substance. In fact it's not.

Vegetable oils are the real dangers.

Saturated fats:

1. Are chemically stable both outside AND inside the body. Vegetable oils ARE NOT. Lipid peroxidation is big problem for those eating a lot of these pernitious oils.
2. Are necessary for stable cellular structures and integrity.
3. For proper protein sythnesis.

Read this: The Skinny on Fats [6]

Hope this gives you some healthy skepticism.