A year ago I lost 50 pounds, I'm 74 yrs old. No secret, just counted calories and did excerise. However, I really like to cook and enjoy a fancy bowel of salad maybe four times a week for dinner. The greens and shrimp or a few pork belly lardons are no great problem, but any dressing oil is 120 calories a tablespoon, and at 700 cals a day allowed, that was a problem.
I found a company, Walden Farms, that makes no calorie salad dressings, and, using their list of stabilizers, set out to make the dressings I like, no-calorie. Gel suppliers for the commercial market, on the web, sell each of the usual stabilizers in "pound" quantities, and I was disappointed until I stumbled on TIC Gels. They sell small containers of various mixes under snappy names and so you can try a few till finding what seems to suit you, for a reasonable initial investment. I tried several and their #702 "Saladizer" is what I now use; about one teaspoon in an initial two cups of water plus whatever additives used, makes a pourable dressing. My final mixes, done in a blender, with a tablespoon of olive oil to absorb the oil soluble components (such as powered cheeses), usually comes to about 10-15 cals/T; not 120. Also, you need a preservative and that seems to be sodium benzoate (1tsp/2C water) and needs a low pH to be effective so I add a dash of vinegar or lemon juice. I found a small quantity of sodium benzoate available at, of all places, SoapGoods.com.
Over the years I also have grown pounds and pounds of basil for making pesto, and now use water rather than olive oil plus the same gel mix. The pesto certainly doesn't have the "oil look or feel," but dressed on hot pasta you really can't tell the difference. And the pesto, with pine nuts, comes in at 10 Cal/T rather than 140.
All of this might seem trite and small, but if you are really trying to lose weight, and are honest about counting calories, hopefully it might help. Substituting for oil is not all that easy.