Diets that high in saturated fats are fine as long as the saturated fats are balanced with unsaturated fats with sufficient Omega 3 fats. Work by Loren Cordain, Ph.D. confirms this. Also, Sally Fallon and Mary Enig, Ph.D have challenged the idea that saturated fats are bad. In fact they argue that since the body makes its own fats (saturated fat) it is absurd to argue that the use of cooking oils would be considered healthy. The body incorporate the fats you eat into the cell membranes. Sally makes a case for eating animal fats including butter.

I would argue that diets lower in fat are more likely to cause Gallstones because low fat diets don't require the gallbladder and liver to expel bile. So bile continues to build and build along with toxins that are taken in.

So eat your fats. The vegans and vegetarians on this site that have found tremendous health most likely have gotten the health benefits not by the reduction in animal foods - but the increase in good quality foods (veggies) and a reduction in plastic foods like margarine, hydrogenated fats found in manufactured food, and refined foods. It is not the reduction in fats. In the short term low fat diets help those of us with sluggish liver/gallbladder since these organs are not making releasing enough bile. But over the long term, low fat diets make this worse. Start slow, but get your fat intake up to keep the liver and gallbladder flushing.

Aside from Dr. John McDougall, the new trend in vegetarianism is to add healthy fats into the diet (thus bring the fat intake up to 30-40% of total intake. See the latest books by Robyn Landes and Andreas Moritz . McDougall wants forbids adding any fats and likes fat intakes to stay at 0-7%. Landis and Moritz are vegetarians that argue against low fat diets. Moritz specfically points out that low fat diets cause gallstones.

Vegetarianism can be healthy, but it must be high in calories to preserve amino acids and contain enough essential fats. For most people though, vegetarianism is a disaster. We have only been farmers for 10,000 years. We were hunters/gatherers for over 2 million years. Vegetarianism could be viewed as a "fad diet" on those terms. Most people just cannot handle huge intakes of carbohydrates.

Well I can attest that I turned Vegan 3 months ago and I just had to have my gall bladder removed. I had a severe case of Pancreatitis and had to be hospitalized.
I have never had any problems before and I am 39!!!
Watch out for the vegan diet or the all protein diet.
I now am a firm believer in BALANCE.
It cost me several thousand dollars to get educated, but I can tell you, you'll learn the hard way also.