Hi Skelly331,
Unfortunately supplements do not tighten up the skin, especially if a large amount of weight is lost and you are left with some flab of skin. To date only surgery treats this.
The Omega fish oils though are a great supplement for other reasons, such as their positive effect on the heart and brain. It is also good for your skin.
Losing weight gradually and exercising may help lessen loose skin flabs, it really depends on how much fat you are losing.
Hope this helps.
Sophia De Monte RPh