Understanding Body Weight

Our body weight is a sum total of all our body organs and tissues which includes muscles, bones, fat, blood and other fluids.
When we refer to our body weight we include all of this & when we say that our weight has increased it is either one or more of these which has increased.
However in most of the cases It is fat and in some cases may be due to edema. Only in case of heavy weight lifters would one see more of muscles.
In any individual, increasing body weight is usually due to accumulating fat. Commonly stored at the abdomen, thighs & around organs like heart, liver etc.

What is LEAN weight?

It refers to the sum of the weight of our organs, muscles, fluids; basically everything except the fat and bones. Therefore we can summarize it as TOTAL BODY WEIGHT = LEAN WEIGHT + FAT + BONES(negligible-always between 1.8- 3.5 kg).
Pregnancy may give rise to an associated weight gain. Ideally one should put on 11-13 kg during pregnancy. If one gains more weight they could have complications during pregnancy. Having a variation of 2 kg more or less is not of great concern. One should consult their physician if they are gaining more weight during pregnancy.
It is a common concern among women that after their pregnancy they may not be able to reduce their weight. But be assured that losing weight post pregnancy is simple and surely possible.

Also there may be a transient swelling up of the body (edema) due to accumulation of fluids and other substances within your body. It is usually due to some underlying condition and can be differentiated clinically or with the help of various investigations which include - a DEXA Scan, blood tests etc.
To know your body in terms of its various constituents do a DEXA Scan. It is the gold standard in Body Composition Analysis and gives a precise and detailed illustration of your body weight along with its distribution in various regions.
However in most cases just knowing that you have a high BMI is more than enough.