WeightWatchers vs. keto: Which is right for you?

Cutting out carbs is the true secret to losing weight. So says the keto diet. But what do experts say? We unpack the difference between these two popular weight-loss approaches.
Published May 31, 2024 | Updated July 10, 2024
A plate of steak with lime slices and other ingredients, creating a delicious and vibrant dish.A plate of steak with lime slices and other ingredients, creating a delicious and vibrant dish.

There’s a “pinch me” moment that occurs when anyone reads about the keto diet. It comes right around the moment they discover they can eat burgers, bacon, and cheese and lose weight quickly. But this very (and we do mean very) low-carb eating plan asks you to lose a lot more than pounds. You have to give up bread, pasta, and crackers, as well as fruit and some starchy vegetables. Is it still worth it? Here’s what you need to know about the keto diet and how it stacks up against WeightWatchers.

What is the keto diet?

The ketogenic (aka keto) diet dials your carb intake way down and your dietary fat intake way up. When you’re following it, you’ll get about 70 to 80 percent of your calories from fat, 10 to 20 percent from protein, and 5 to 10 percent from carbohydrates. And it’s quite a departure from what most health experts recommend. The current Dietary Guidelines for Americans recommends 45 to 65 percent of calories come from carbohydrates while the World Health Organization advises that total fat intake should not be more than 30 percent of your total calories (and that saturated fat should not be more than 10 percent of your total calories).

Eating the keto way also means there are a lot of foods on the “not allowed” list. “You’ll mostly avoid all grains, milk, yogurt, fruit, legumes, and starchy vegetables, like sweet potatoes, winter squashes, peas, and corn,” explains Amy Goodson, RD, a registered dietitian based in Frisco, Texas. While some of these foods can be included carefully in very small amounts (think a quarter cup of sweet potato), they cannot be eaten regularly.

Instead, you focus on:

  • Fats: Avocado, olive oil, butter, coconut oil, nuts
  • Proteins: Especially fattier cuts of meat like beef or bacon or fish like salmon
  • Non-starchy vegetables: things like bell peppers, broccoli, cauliflower, and cabbage

Breakfast on keto may look like a cheesy omelet cooked in butter with avocado; lunch could be a bunless burger (with bacon if you want); dinner might be a creamy chicken dish served over cauliflower rice.

How does the keto diet help people lose weight?

It all comes down to that extremely low carb intake and what happens in your body when you lose weight. Normally your body turns carbohydrates into glucose, which it then uses for energy. But when you don’t eat enough carbohydrates, your body has to adapt. “It stops using glucose for energy and starts using fat instead,” says Goodson. With no glucose, your body first uses up any glycogen (glucose that’s been stored in your muscles and liver) and then, when that’s depleted, the body ultimately turns to fat for energy. Your liver breaks down fat into a type of acid called ketones, which enter into your bloodstream and act as a source of energy. When your body primarily runs on ketones, you’re said to be in the state of ketosis.

And it’s being in ketosis and burning up fat for energy that’s seemingly the key to weight loss with the keto diet. For example, a small 2019 study found that 12 weeks of a ketogenic diet led to an average of 24-pound weight loss in women and an average of 39-pound weight loss in men (all participants had obesity). The people on the diet also reported less emotional eating. In another meta-analysis, people with diabetes who went on a keto diet decreased their BMI by an average of about three points, reduced their waist circumference by an average of about 3.5 inches, and lost an average of around 19 pounds.

The need to stay in ketosis is why keto is not a high-protein eating plan. Your body can convert some of protein’s amino acids into glucose, says Goodson. Therefore, eating too much protein can prevent you from entering into ketosis or kick you out of it, impacting how much weight you’ll lose.

Is the keto diet nutritious?

The keto diet leaves a lot off the menu, which can impact how balanced your overall diet is. Though you don’t have to eat whole grains to be healthy, they are a major source of fiber. Without a carefully planned keto diet where you ensure you’re getting enough fiber through foods like vegetables, chia, and flaxseed, you can become constipated.

While the keto diet specifies the amount of fat to eat, it doesn’t give rules about the kind of fat. For that reason, it’s within the keto guidelines to eat a diet packed with foods high in saturated fat, such as bacon, butter, coconut oil, and fatty meats. Diets high in saturated fat can raise your “bad” LDL cholesterol levels, which can contribute to an increased risk for heart disease.

How does WeightWatchers differ from the keto diet?

WeightWatchers programs — which include the Points® Program, Diabetes Program, and GLP-1 Program— don’t forbid carbohydrates or encourage high fat intake — in fact, there are no off-limits foods. Instead, WW guides members toward an overall eating pattern that is higher in healthy fats (fats with more unsaturated fats than saturated fats), lean proteins, and fiber, while guiding you towards an eating pattern that is lower in calories, saturated fat, and added sugar. WeightWatchers is designed to be a lifestyle, so each program is specifically tailored to the individual person. It is designed to be a way of eating that is enjoyable and long-lasting.

On WeightWatchers Points Program, for example, you get something called a Points Budget that’s based on your sex, weight, height, age, and activity level. Points are determined by a food’s makeup: Calories, added sugar, and saturated fat increase the Points value, while unsaturated fat, protein, and fiber in foods tend to lower the Points value. These Points are divided into daily and weekly values, which makes following the plan flexible (and more realistic). If you go over your daily Points values, you have a reserve of Points to use in your weekly Points. If you use more Points one day, like when you’re out to dinner or attending a birthday party, and you can still hit your weekly goals by staying within your weekly Points values.

This works: Randomized, controlled studies have found WeightWatchers to be more effective for weight loss over six- to 12-months compared to do-it-yourself approaches, physician counseling, and professionally delivered behavioral weight-loss programs. WeightWatchers is also the number one doctor-recommended weight-loss program, based on a 2020 IQVIA survey of 14,000 doctors who recommend weight-loss programs to patients.

Are there advantages to the keto diet?

Have a neighbor or friend who swears by the keto diet? It’s probably because it helped them lose weight super fast. “Carbs can cause the body to store extra water,” says Dr. Caroline Cederquist, MD, a bariatric medicine specialist at Cederquist Medical Wellness Center in Naples, FL. “When carbs are limited and depleted, that water weight is shed fairly quickly.” In addition, being in ketosis may increase the amount of calories your body burns per day, decrease appetite, and burn fat, all of which can contribute to weight loss. Seeing that drastic change on the scale in the beginning can be motivating.

Separate from weight loss, the keto diet also shows promise in improving blood sugar management for people with diabetes. Research shows following a keto diet can help lower fasting blood glucose, A1c (an average of blood sugar over time), triglycerides, and total cholesterol. This is likely because eating fewer carbohydrates leads to less fluctuations in glucose (a.k.a. blood sugar). Other research on adults with type 2 diabetes found that among a group who followed a diet that put them into ketosis for one year, 94 percent were able to reduce or stop insulin therapy.

That said, the keto diet isn’t the only way of eating that can improve blood sugar. After six months on the WeightWatchers Diabetes Program, participants lost an average of 5.7 percent of their weight and reduced their HbA1c by 0.75.

What are the disadvantages to following a keto diet?

While keto can deliver on short-term results, it tends to be difficult to stick with over time due to its restrictive nature, especially if others in your household aren’t also eating keto or you love to dine out. One big reason it’s tough to maintain: Many people like carbohydrates, says Goodson. “Any restrictive diet is difficult to follow long-term, especially when you have to restrict what you eat wherever you go,” she says. What’s more, a weight plateau is likely once you’re out of the initial period, and when that happens you’ll need to make further adjustments with diet or exercise. “If you’ve started out extreme, where do you go from there?” Goodson asks.

The restriction can also set the stage for a negative relationship with food, Cederquist points out, possibly triggering cravings, binge eating, and yo-yo dieting. “While the thought of quick weight loss is alluring, it’s best to lose weight in a healthy and sustainable way,” she says. “I generally recommend starting with one small change at a time for long-term success.” For example, you might start out by adding one fruit or vegetable to each meal, taking a 15-minute walk after dinner, or drinking an extra two cups of water throughout the day.

There are also physical side effects that people experience on the keto diet, including the keto flu, a constellation of symptoms that happens as your body adjusts to being in ketosis. You might have headaches, dizziness, nausea, muscle cramps, and rashes, among other issues.

What should you consider when choosing between WeightWatchers and the keto diet?

Keto and WeightWatchers are drastically different diets. Keto focuses on restricting carbohydrates and, by default, removes entire food groups from your diet. WeightWatchers, on the other hand, says that no food is off limits, prioritizes an eating pattern in line with the Dietary Guidelines for Americans, and allows for a gradual, but sustainable, way to lose weight and maintain weight loss.

Ultimately, the weight-loss plan you choose should take several factors into consideration, such as your lifestyle (do you travel a lot or love to socialize with friends and family over meals?), food preferences, health history — and even your personality. “Asking yourself what type of diet you prefer is helpful for finding an eating plan you’ll enjoy and sustain,” says Cederquist. What you don’t have to do is follow something because it’s trendy or because your coworker or friend said it worked for them. This is about you.