Is skipping meals a bad idea — or a secret weight-loss weapon? Should you eat low fat, or high fat? You probably could eat less added sugar, so should you eliminate it completely?
With so many competing — and often contradictory — diet trends, it can be tough to cut through the hype to find a healthy-eating plan that works for you. Check out the evidence behind each of these four increasingly popular eating styles to uncover the real deal.
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.
How it works: Bring on the bacon. This high-fat, very low carbohydrate diet typically means eating fewer than 50 grams of carbs a day — less than four slices of bread's worth.
What it promises: Getting most of your calories from fat forces your body to use different energy pathways. Instead of carbs for energy, the body burns fat, entering a state called ketosis.
The upsides: While the precise mechanisms are unclear, ketosis is thought to have brain-protecting benefits: As many as half of young people with epilepsy had fewer seizures after following the diet. And some early research suggests it may have benefits for blood sugar control among people with diabetes. An upcoming study will look at the ketogenic diet as a weight maintenance strategy.
The downsides: While the research is exciting, there's very little evidence to show that this type of eating is effective — or safe — over the long term for anything other than epilepsy. Plus, very low carbohydrate diets tend to have higher rates of side effects, including constipation, headaches, bad breath and more. Also, meeting the diet's requirements means cutting out many healthy foods, making it difficult to meet your micronutrient needs.
Mayo's verdict: While the ketogenic diet may be recommended for some people with uncontrolled epilepsy, the high fat content — and especially the high level of unhealthy saturated fat — combined with limits on nutrient-rich fruits, veggies and grains is a concern for long-term heart health.
How it works: While there is no single anti-inflammatory diet, the general approach is a balanced diet full of fresh, wholesome foods. The diet calls for lots of colorful fruits and vegetables, whole grains, fish, tea (instead of coffee), and even dark chocolate and red wine. Fast food? Off the menu.
What it promises: Eating whole, unprocessed, largely plant-based foods is thought to fight chronic inflammation and help counteract stress and environmental toxins. In turn, this may lower your risk of heart disease, cancer and Alzheimer's.
The upsides: Fresh fruits and vegetables? Check. Whole grains? Check. Healthy omega-3 fats? Check. Chocolate and wine? Double check.
The downsides: Learning to prepare fresh, plant-based foods can be more time-consuming than relying on pre-packaged or fast food.
Mayo's verdict: Just like the Mediterranean diet it's based on, this approach to eating is nutritionally sound and not overly restrictive like some other diet trends.
How it works: There are two common approaches to fasting: One is to eat very few calories on certain days, then eat normally the rest of the time. The other involves eating only during certain hours, and skipping meals for the rest of each day.
What it promises: Even with free eating periods, fasters tend to take in fewer calories overall, resulting in weight loss. In addition, advocates believe that intentionally depriving your cells of calories may slow the progression of certain age-related diseases.
The upsides: Some people find it easier to have bulletproof willpower for just part of the time than to eat more moderately all of the time. Several small studies have found lower blood sugar, blood pressure and cholesterol levels with fasting.
The downsides: Larger, long-term studies are still lacking, so most of the proposed benefits are theoretical or based on animal research.
Mayo's verdict: There's simply not enough research (yet) to support or debunk this trend, and shortening your eating window may make it difficult to get the vitamins and minerals you need. Athletes especially may find it difficult to fuel and refuel appropriately for an active lifestyle.