hi im new.im 16 yrs old male height 5'7. my routine is only 40mins on the treadmil i burn 1400 calories a day,and i see that i can lose 4-5LBS a week,so thats 16-20LBS a month is that dangerous? or is it ok?. and is building up muscle is good to lose weight too? thats all TY

Just know that you cant lose weight at that rate forever. One or two months max, then it will slow down. Mainly because I wouldnt say you are extremely overweight. However if you were 300lbs I would say you could sustain that weight loss longer.

Any strength training?

Hi Demxy,

I wouldn't say it is dangerous, as long as you are consuming plenty of calories and water, and you don't allow yourself to feel too tired.

I was losing around 14 pounds a month for about 3 months or so last year [was 322 lbs, 6'3" tall].

Building up muscle is great for burning calories faster - the extra muscle may mean you don't lose weight as fast, as muscle is heavier than fat, but which would you rather have?

Also more muscle means higher metabolism, so you will burn the calories off much faster when you do cardiovascular exercise such as walking/running on your treadmill.

Hope this info helps, Mike.

To answer you indirectly:
Losing 3-4lbs a week is bad because you're obviously starving your body, forcing it to possibly go for muscle and vital organs. And for vanity it's just not letting your skin have a chance to contract right, ie loose skin.

If you're eating less than you need to maintain your current weight, you can't expect to build muscle, can you ? But weight training can help lose fat and maintain muscle(Which you will lose, no matter) during weight loss.