2. 98年にWHO(世界保健機関)が発表した基準と、それを参考に日本人の体型および体質に合わせて作った日本の基準の二つがあります。
長さは2,000字以内とします。
とします means consider something to be something. Here, it literally says, consider the length (of the essay) to be within 2000 words. But if you translate it into English proper, it's the same as です in this instance.
The WHO one is tricky so let's break it down. The basic sentence is:
二つがあります。There are 2 of something. What is that something? The first one is:
98年にWHO(世界保健機関)が発表した基準
The standard announced by WHO in 1998.
The second is:
それを参考に日本人の体型および体質に合わせて作った日本の基準。
Lets break this one down. First of all, the basic part if this sentence is 日本の基準。so it is a Japanese standard. The clause preceding describes how it is made and there are 2 parts.
それを参考に。それ refers to the WHO基準。the rest of the sentence is a shorthand means 'as a reference', それを参考にして would be the complete clause. I would translate it as 'based on' however. So this part means based on the WHO standard.
日本人の体型および体質に合わせて作った
Here, にあわせて is the causative form of 合う. It means to make match. So this translates as 'matching Japanese body shape and constitution.
NB: に合わせて is also a set phrase meaning to combine but I think it makes more sense that this is the causative form of 合う
Bang the whole sentence together and you get the following.
There are two standards, one of which was announce by WHO in 1998, the other is a Japanese standard based on the WHO standard matching the body shape and constitution of Japanese people.
Japanese is very hard to translate into English. Word order is almost complete backwards. Best to absorb the sentence directly.
その数値が大きいほど脂肪の量が多いことを示しています。
This is literally saying, the bigger the number, the more fat you have. Not fat as in physically fat, but it could be internal body fat.