近20年来，各方面的调查表明：青少年的体质不断下降。请你以“How to keep healthy”为题，写一篇80词左右的短文，说说你的看法和建议。开头已给出，不计入总词数。
1.体质下降的原因。如：eat too much junk food，have too much homework……
2.合理的健康建议。如：should do more exercise，eat a balanced diet(饮食平衡)，enough sleep……
How to keep healthy
Nowadays students'physical fitness is declining year by year.I think there are some reasons.
Students have too much homework to do，so they have little time to have sports.Some students eat too much junk food.That's also bad for their health.
Then，how to keep healthy?Here is some useful advice.First，students should do more exercise.Second，students should eat a balanced diet.They should eat more vegetables and fruits，and try to eat less junk food.Finally，enough sleep is also very important.