Vegan diets are hard for many people to stick with long-term, but studies show that this way of eating can translate to weight loss.

Vegan is the strictest type of vegetarian diet -- you choose only foods from plant sources, such as vegetables, fruits and grains, and avoid all animal products.

In a small trial done in South Carolina, people who followed a vegan plan lost about twice the weight of non-vegetarians and even those who followed a more varied vegetarian diet.

People on a vegan diet often have a lower body mass index, eat the least amount of fat and the most amount of fiber, and get more macronutrients than those on other diets.

Yet it often takes extra effort to get enough protein and meet calcium needs. Despite the challenges, if you want to jumpstart your weight loss, a three-week vegan trial might just be what the doctor ordered, according to the nonprofit Physicians Committee for Responsible Medicine (PCRM). And you might even use it as a transition to a less-meat-focused diet afterward.

As a way of life or to continue weight loss, you may find it easier to stick with a vegetarian plan that includes low-fat dairy, eggs and/or seafood. In fact, there are many variations, one of which might work for you.

Vegetarian by definition:

Vegan: No animal products allowed -- no meat, seafood, poultry, eggs and dairy.

Lacto-vegetarian: Dairy allowed but no meat, seafood, poultry and eggs.

Ovo-vegetarian: Eggs allowed but no meat, seafood, poultry, and dairy.

Lacto-ovo vegetarian: Dairy and eggs allowed.

Pesco-vegetarian: Fish and seafood allowed, but no meat or poultry.

Semi-vegetarian: Mediterranean-style diet based on fruit, vegetables, fish and olive oil with small amounts of chicken, dairy products, eggs and red meat allowed once or twice per month.

Give one or more a try until you find the happy medium for you.