I'm 16 At 140lbs And I Want To Lose 35-40 Pounds. How Can I Do That?

You are entering into some severe damaging to your health. You are too young to make this decision about you weight loss. Doing unnatural things to lose weight can damage you for life. A sudden drop in weight can distort your body's normal functions, and even send you into cardiac failure. This is a subject you should discuss with your mother, who can assist you in you desire to lose weight. I am not sure anyone will want to assist you reach your desired weight of one hundred pounds.  Also please, think about what you just said.  You want to lose for a model pageant. Your health is best when you do what is necessary to promote an even healthier life, including your mind. Being a model is not worth risking your health.  Please speak with your mother or school nurse.
I am hoping you will give this more thought.

Honey did they say you are to required to lose that much weight?
It all depends on your height too not just how heavy you are. Go type in dietary nutritions and it'll show many ways to eat healthy and to lose weight. I believe you're still young to take any diet pills. You can get onto any diet supplement site and they'll also have dietary plans for you to follow. You'll learn how to eat healthy and then choose your own food to make your meal. There's still exercises you have to do too that goes along with losing weight and being healthy at the same time.
I'm sorry I don't have a direct site for you go see because every individual has their own preferences. Take care and be healthy at the same time, don't starve. I know you wont.

OK...first of all:

The way you lose weight at 16 is the same way you lose weight at any other age.

However,

Keep in mind that losing 35-40 pounds may not be healthy given your height (which you haven't provided)...or sex for that matter (I'm assuming you're female).

nevertheless, the way you lose weight is by sustaining a caloric deficit over time.

Take the amount of calories your body needs to maintain it's current weight by this formula:

bodyweightx15... So 140x15 = 2,100 calories/day.

Now...to lose 1 pound, you need to be in a deficit of 3,500 calories total....eat 500 calories less than your maintenance daily(1,600 calories/day) and you will lose 1 pound/week.

To lose 2 pounds/week, add 1 hour of cardio on an elliptical to burn an additional 500 calories daily.

Losing 2 pounds/week (not including weight loss stalls), you could see 35-40 pounds lost within 20 weeks or 5 months.

Make sure you're eating satiating yet low calorie foods such as vegetables/fruits and lean meats instead of processed foods.

These are just some basics, but to really be successful you need to learn more on how to implement a proven diet/exercise regimen.

Sweetie, unless you are 4'9 - 5 ft even, that is WAY too low... Your going to kill yourself, not look better.. Wow