What you do: The South Beach diet is a three-phase program designed by cardiologist Arthur Agatston in 2003. In the first phase, you cut out all carbs, fruits, and alcohol. In phases two and three, you gradually add some of those foods back in (as far as carbs go, you’re only supposed to eat whole-grain ones). It’s important to note that this is a commercial diet, so you may have to buy the official plan and materials.

What the science says: The diet focuses on whole foods, which is good since studies have shown this is the best approach for weight loss. Cutting out any of the food groups could leave you lacking nutrients, though. Some people on the diet have reported ketoacidosis, a condition with symptoms including bad breath, dry mouth, tiredness, dizziness, insomnia, nausea, and constipation. Studies have found South Beach diets (or those very similar to the name-brand version) could help people lose weight in the short-term, but researchers haven’t followed people long-term to see if it helps them keep the weight off. The problem here is that while the second two phases of the diet are somewhat reasonable, the first phase is very restrictive, so some people might have trouble sticking to it.

What you do: On the new Weight Watchers (the one Oprah has advertised lets you eat bread), their SmartPoints program assigns foods points based on their nutritional values. You get a set number of points per day depending on your height, weight, activity level, and how many pounds you want to lose. The plan can cost between about $20 and $70 a month, depending on whether you pay for add-ons like coaching or meetings.

What the science says: Research has overwhelmingly positive conclusions about Weight Watchers’ sensible rules, and the new program is even more in line with what nutritionists recommend. Participants in a clinical trial on the plan for a year lost nearly 7 pounds. And other studies have found Weight Watchers members also tend to lower their heart disease risk and blood pressure. An interesting analysis found that participants on Weight Watchers for a year typically paid $70 per pound lost, but gained $54,130 in quality of life improvement.

What you do: There are many different kinds of vegetarians, but generally, you don’t eat meat or fish.

What the science says: In observational studies, vegetarians tend to weigh less than their carnivorous counterparts. Cutting meat from your diet could reduce your environmental impact as well, research has found. You have to make sure you get enough nutrients (especially protein) from other sources like nuts, grains, and dairy, though. But the benefits could be considerable: Studies have found that vegetarianism is linked with lower chances of heart disease and cancers, and higher chances of living longer.

People also ask:

How do I diet?
Here are more tips from Dawn Jackson Blatner, RD, author of The Flexitarian Diet:
  • Eat vegetables to help you feel full.
  • Drink plenty of water.
  • Get tempting foods out of your home.
  • Stay busy — you don’t want to eat just because you’re bored.
  • Eat only from a plate, while seated at a table. …
  • Don’t skip meals.