Whole30

How it works: For 30 days, no sugar, alcohol, grains, legumes, dairy or treats in general are allowed. What's on the menu? Moderate amounts of meat, seafood and eggs; vegetables aplenty; some fruit; and natural fats such as nuts and avocado. Herbs and seasonings are A-OK.

What it promises: A reboot for your eating habits and your cravings. Plus, the founders say that eliminating these food groups may help with a number of ailments they blame on food sensitivities, such as skin problems, digestive issues, low energy and chronic pain.

The upsides: No doubt the Whole30 is strict. But for some people, a black-and-white list of rules stating what you can — and can't — eat, makes it easier to follow (at least for 30 days). Plus, the growing popularity makes recipes and meal plans easy to find. Cutting out snacks and processed foods such as chips and crackers is part of the plan.

The downsides: Though the internet is full of anecdotal success stories, there's no scientific evidence of health benefits — particularly in the long term. Most people return to their previous eating habits after completing the challenge.

Mayo's verdict: Not only does it cut out foods that most Americans should eat less of, like added sugars, but it also eliminates healthy foods, including whole grains, dairy and legumes. A more sustainable approach: Don't cut out food groups. Enjoy the variety, including dessert — as long as it's occasional.