Can't help much with the wieght loss thing athough when I need to shift some weight (have just lost 3/4 of a stone) I use the low-fat diet which seems to work well for me. I'm not sure how good it is for your health doing it long term though.
But the insomnia. Can you identify what triggers it? Are you worrying about things? If so, write them down as a sort of 'to do' list for the next day. Sometimes the worry about worrying (iyswim) can be enough to stop you sleeping.
Check your room. Is it too hot/cold? Are your bedclothes comfy? Is your bed comfy? Do you have a tv in there? If so, don't watch it.
Stop drinking any caffeinated drinks after about 4 or 5 pm. DOn't drink alcohol in the hope that it'll send you off to sleep- it may do for one night but it'll be poor sleep and will disrupt subsequent nights. Don't eat anything heavy too late in the evening. Have a light snack later on with a cup of warm milk (I usually have a couple of very plain biscuits).
Have a warm - or hot- bath. Switch off the television half an hour before going to bed/ the time you plan to be sleeping. Read a gentle book.
MAny people use lavendar pillows (I hate the smell, myself) or drops of lavendar oil on a hanky near the bed. Try chamomile tea. Actually some gentle exercise is extremely helpful.
Erm... what else have I tried over the years.
Try a change of scene. SLeep upside down in the bed. Have a ritual as a 'trigger' for your mind to know that it's time to sleep(works for babies, can also work for adults)
Get a bit cold before getting into bed and take a hot water bottle. The sudden change in temperature can help.
Try herbal sleeping pills. I sometimes use Kalms herbal which are quite good.
Failing all of that, go to your gp. Don't be fobbed off with advice of a hot drink. Tell him you've done all that and need more help. I used Zopiclone for several years (not all the time, just for the periods when my insomnia was at its worst) and it was a lifesaver.
Get your sleep sorted first. Anything else will seem much too hard if you're struggling to stay awake.