It would not be a low fat diet, either. But, it would be very low in saturated fats, which means that you might have to give up some of your favorite foods.
If you are overweight, no more than 30% of your total caloric intake should come from fats. If you decide to follow a fish oil diet, 20-40 fat calories would come from the supplements. But, research indicates that those calories must not count.
The study looked at the effects of adding 44 calories a day to an already overweight person's diet. Normally, that would cause a weight gain of about a pound every three months or so. But, the volunteers followed in the study did not gain weight.
There's more to learn if you want to follow a fish oil diet, including how to choose a good supplement. I have found the best value of fish oil product made from Hoki. A fish found in the deep water of the pristine ocean off the coast of New Zealand, that is naturally high in DHA and EPA for less than $20 a month.
Whatever product you buy the best fish oil is always pharmaceutical grade fish oil supplements because your health depends on it, so why not buy the very best? That's what I do.