Depends on the 15 year old, where they are in development and what their goals are. A well balanced food plan (not the same as a diet, diets are temporary, food plans are life styles) would consist of a diet high in veg and fruits along with some grains, some meats and small portions of fats and added sugars. If we are speaking in terms of weight loss (which is often called a diet) then we have to consider what the 15 year old is already eating, how they (portions and how often during the day) and deal with aspects of the diet there. When it comes to weight loss the problem is no so much how much they eat, but what they eat, when they eat and then what they do in the form of exercise. Lowering added fats and added sugar and a small increase of exercise during puberty will have a larger over all impact on weight and health than a crash diet for the short term. Fat should be lost gradually,we are talking about less than 5 pounds of fat lost over each two week period. For a person 50 pounds over weight we are talking in terms of (at most) 140 days to lose 50 pounds. (20 weeks, or 5 months - that is assuming that they are exercising and eating a proper diet each and every day. And then that much weight loss in that short of a period is still considered unhealthy. Ideally one should seek to lose 50 pounds of fat over the course of 6 to 9 months - and then it should not show up on the scales as 50 pounds lost - it should show up as about 10-20 pounds being converted to muscle mass and organ mass in a developing teenager - if not more. Going on a starvation diet (low-cal diet) or any of the fad diets is more dangerous for teens than adults. Most of those programs include the loss of many nutrients and vitamins and minerals which can have a moderate to severe impact on the person later in life. There is direct and indirect links to teenage diets having a huge impact later on in life such as osteo (bone) issues, joint issues and of course the well known and dreaded diabetes, stroke and heart attack. Even if you do go to a healthy inclusive diet after puberty the theories are growing and being substantiated that diet during puberty affects how the body will process food and the nutrients for the rest of the life of the patient. Low added fat and low added sugar means to reduce the consumption of fat (oil, margarine, butter, shortening, bacon fat) and the use of sugar (For instance kool-aide calls for 1 cup of sugar should be reduced to 3/4 or 1/2 cup sugar - still tastes great, less sugar) Many people prepare foods, like corn on the cob, with adding stuff like sugar. Pasta is often cooked with oil - oil is not needed when cooking pasta - a bit more stirring of the pot and a good rinse in clean hot water reduces the stickiness of pasta more than a tablespoon of oil will. Of course cutting back on fastfood, junk food and replacing those with healthy snacks like fresh veg and fruit, like low fat/low sugar baked goods. I make muffins which take half of the sugar, and use apple sauce (no sugar added) instead of oil or shortening - over half of the calories and they are melt in your mouth tasty. The other half of the equation is exercise. Exercise does not require going out for sports or joining a gym. Exercise can and should include walking more. For instance parking as far away from the store doors as possible, and to go up and down every single aisle as you shop - yes even those that you don't need to go down - you are increasing the amount of exercise you routinely do - granted you may not burn that many calories doing that once, but if you do it every time you shop the calories burnt stacks up to huge numbers. At school take the longest route from class to class, maybe even do a fast walk or a jog. Take a walk around the block every night - its just a minor increase of exercise but it does pay off in the long run.

Like the othere person Said it depends on what the 15yr old dose. Is he in sports? What kind of sport one that burns lots of calories of a musel building sport?

It kind of also depends on your metabolism- for example, im 15 yrs 6 mnths, and weigh 167 pounds. Plus im only 5 foot 7. And yet i exercise a LOT. Steak is the norm rather than the exception for me. And im one of the fastest sprinters and can lift 4th place in my pe class of 35 students. And yet I have body fat easily visible- it kinda represents my diet (i eat a LOT of meat) and the fact that my matabolism doesnt seem to be build for a more slender build. I suggest, if you have some weight to lose and it wont go away, join the gym and run on the treadmill. most teens cant run for more than 7 minutes straight, but with the right exercise that time can increase while burning calories and fat. And when you dont, take every opportunity to go for a LOOONNNG swim too

The best diet is to stop worrying about that, you're just 15 come on!! Leave that to the old people. But do try to avoid fast food and junk food. That's no good.