I'm 18 (I turn 19 in January), I'm 169.5 cm tall, male, 75.2 kilograms. My doctor today said he wants to up me to 1400 calories for 3 days, then 1600 for the next three, then finally sustain 1800 a day with my current workout regiment (an hour and 15 minutes a day on my exercise bike). He said he wants to see a weight gain and that my other weight gains are likely my body making up for the net caloric loss of 2400 calories per day when I was only eating 1100-1200 calories a day. He said that my body is sort of panicking and converting more glucose into fat instead of my body using the recommended 1800 calories as energy. I'll see what happens over the next few weeks. He wants me to get back up to around 77 kilos and then 6 months from now he said I will have lost (if my workouts stay similar) those 7 kilos and be down to an ideal weight of 70 kilos. I just need to stop weighing myself every day. I'm going to go to once a week to keep track and I'll let you guys know how it goes. Thanks again.

OK - your current Body Mass Index is 26.1, which places you slightly into the "Overweight" category (note: Body Mass Index is simply a ratio of weight to height, and NOT the same thing as body fat percentage).

You are currently in the 72nd weight percentile when compared to US averages (in other words, 72 percent of 169.5 cm tall, 19 year old US males weigh less than 75.2 kg).

The "Harris-Bendict" formula for estimating metabolic requirements says that if you are:

1) Sedentary (little or no exercise), you need 2177 calories per day.
2) Lightly Active (light exercise/sports 1-3 days per week), you need 2495 calories per day.
3) Moderately Active (exercise/sports 3-5 days per week), you need 2813 calories per day.

Of course, these are just estimates, but this formula has been in use for quite some time now because it's proven reasonably accurate for most people.

Based on this, it sounds like you're trying to lose weight far too quickly. If you exercise regularly, and eat around 2000 calories per day, you should see a steady rate of weight loss. But please note that weight loss is rarely linear - there will always be plateaus where you're stuck, and times (like around the holidays) when your weight goes up for a few weeks.

The fact that you are "panicking" about it may indicate an eating or anxiety disorder...please ask your doctor about this.

70 kilos would be a good target weight for you. But, at your age, and if you are interested in cycling performance, you could aim lower and still be in the "healthy" weight range. 66 kilos would give you a BMI of 23.0, and you would feel much stronger when climbing on the bike.

Best of luck!

sorry I was unclear about the panicking. I'm not saying I'm panicking about losing weight. I was trying to say that my body is being told I'm not taking in enough calories so "it's" panicking and storing what food I do eat as fat b/c it thinks I'm starving.

I can not resist sharing this TRUE experience.
I normally eat a diet very low in salt.
Last Christmas Eve morning I woke up weighing #130. At very little during the day but on Christmas Eve we had soup and crackers, but then on Christmas Day I had ham, olives, pickles, and pretzels. On Decemver 26 I weighted #142!!!!!!!!!! You should have seen my legs walking into the gym .....they were so.......bloated. I swear you could actually see all the fluid under the skin. It took about 4 days and all the weight was gone!

I weighed 172# two days ago. I had mexican food with lots of Salsa (sodium) the other night. Spent an 1.5 hours on the trainer the next day. The following morning, I weighed 177#. Defnitely water.
Today I spent another hour on the trainer, and drank a good quart of Gatorade.

Now, back down to 173#. Go figure.

Just to add a little more confusion to the discussion:

Our young man is 18, almost 19. I believe that it is developmentally normal to gain weight at this age. It's really the last "symptom" of puberty, and it's well enough known to have a common name--"freshman fifteen"--so called because college students often gain about 15 pounds in their freshman year. This is naturally a more difficult time of life to lose weight because you are bucking your hormones, but it can be done. Just stick with the diet prescribed by your doctor. It sounds like he put some real thought into it, and he seems to know you pretty well. Also, I know from my own experience that you are right that many of us should not weigh in more than once a week.