Hi Rina (verskoon tog dat ek u in Engels antwoord)
I think that maybe that as we get older our body has naturally protective mechanisms that unfortunately clash with how we are conditioned to want our bodies to look, so it feels as if our body is going against our wishes, when actually it's doing what is naturally healthy for it. For example carrying a bit of extra fat as you get older is apparently protective against osteoporosis and it also helps us reduce wrinkles. Sadly though so often, our wishes are opposite those that are protective for our body. 6 kg's of weight gain really isn't an enormous amount, even if it feels to you like it is. You might like to use our body fat calculator (check our freebies tab) to see what your percentage body fat is.