Earlier this week U.S. News & World Report released their rankings for 2018’s best diets, and one of the top spots went to a lesser-known plan, called the HMR Program—it tied with Weight Watchers in the “Best Fast Weight-Loss Diets” category.

So what is the HMR Diet? It’s not as new as you might think.

Formerly known as Health Management Resources—though now titled “The Healthy Solutions Diet,” the HMR program was developed over three decades ago by behavioral psychologist Lawrence Stifler. The program involves two phases.

Phase one is the “Quick Start” phase: participants aim to lose weight as quickly as possible, eating lots of fruit and vegetables, as well as HMR-branded food that are shipped every two weeks. Phase one is based on a “three-two-five” structure: a minimum of three HMR shakes, two HMR entrees, and five 1-cup servings of fresh, canned, or frozen produce.

Participants can expect to lose 1 to 2 pounds each week, with an average weight loss of about 23 pounds in the first 12 weeks.

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When participants reach their goal weight, or want less structure, they move on to phase two, which lasts for 4 to 8 weeks. In phase two, participants receive HMR-approved foods monthly and slowly work in other healthy, low-calorie food options. The goal in this phase is to wean off the HMR program and begin to make healthy choices.

Participants are also encouraged to exercise and burn 2,000 calories each week. To foster accountability, users have weekly phone calls and counseling with registered dietitians and exercise psychologists.

In a 2015 study in the Annals of Internal Medicine, researchers took a look at multiple commercial weight-loss programs, including Weight Watchers, Jenny Craig, Nutrisystem, Atkins, and HMR. HMR participants lost 4 percent more weight in the short-term than those in the other diet programs, but longer-term results were mixed.

The bottom line: This diet can work for people who don’t enjoy meal prepping—the HMR diet delivers all the low-cal, heat-and-eat entrees and shakes; all you have to do is add in your favorite produce. This is also convenient for when you need to pack lunch for work, or whip up dinner in a hurry. Bonus? You can have as much fruit and veg as you want, so you’ll never feel famished.

The downside? Phase one encourages participants to avoid restaurants and most social situations altogether to “avoid temptation”. You also can’t drink any alcohol in phase one, so if you’re a social butterfly you may want to choose another plan.

Also, the plan can be pricey: The 3-week HMR starter kit costs $271.50, and the standard 2-week reorder kit costs $185. Individual shakes, cereals, and soups can be purchased online and run between roughly $2 and $2.50 per serving, and entrees cost $3.70 per serving.