DIETS —And Their Downsides
Want to shed pounds in the New Year? Here are seven popular plans—and a doctor’s view of the pulses and minuses of each.
That gut, that butt, those thighs, that size—does a January glance in the mirror tell you it’s time to shed pounds? Never fear. Scrolling through social media will bombard you with suggestions from friends, brands and influencers alike. “Keto,” “paleo” and “raw food” are just three of the trendy names you’ll hear. Doctors, of course, say that healthy, balanced and restrained eating combined with exercise over the long term is more effective than “fad” diets. But it can be reassuring to get with a program that has a name.
“These diets have simple rules and promise results, and that’s part of their draw,” notes Raunak Singh, D.O., who practices family medicine and sports medicine at Bergen New Bridge Medical Center in Paramus. “There’s a psychological appeal, because they claim to be easy and to make you healthy and slim. They cultivate a quick-fix mentality, and they treat the diet like it’s a short-term commitment instead of a permanent, healthy lifestyle change.”
Is there any diet Dr. Singh sings the praises of? BERGEN wanted to know, so we asked him what’s great about seven popular plans—and what’s not so great:
KETOGENIC DIET
Developed by Russell Wilder, M.D., in 1923 as a treatment for epilepsy, the ketogenetic diet (often shortened to “keto”) operates off a “4:1” ratio—just one part of carbohydrates is consumed for every four parts of fat. In essence, it promotes eating a very small amount of carbohydrates (the main nutrient in foods such as bread and pasta) and replacing other carbs with fats. “You increase your fat intake to a point where you’re putting your body in a state of ketosis, which means it’s using fat as its main energy source,” Dr. Singh explains.
PROS: One thing remains consistent in studies of the keto diet, according to a 2022 study published in Frontiers in Nutrition entitled “Fad Diets: Facts and Fiction”: It’s effective in improving quality of life and seizure frequency in epileptic patients. It also has been associated with a “neuroprotective action” effect against neurological illnesses including Alzheimer’s disease and Parkinson’s disease, because it encourages the production of ketones in the liver, which supply energy to the brain—though this benefit is still being studied. Cutting carbs to this extent can also encourage short-term weight loss.
CONS: However, says Dr. Singh, “a lot of that initial weight loss is water weight.” There are also possible health complications from going all-in on keto. In the short term, the 2020 paper “Consumer Reports of ‘Keto Flu’ Associated with the Ketogenic Diet,” also published in Frontiers in Nutrition, describes that affliction—those who have recently started keto often experience lethargy, low blood sugar, nausea and gastrointestinal discomfort. Says Dr. Singh: “People also don’t always look at the kind of fat they’re eating. So their diets may be high in saturated fats, and that comes with the risk of raising cholesterol.” He also encourages caution about diets that focus on totally restricting one food. “Be wary of anything that cuts out something entirely or tells you to only eat one thing,” the doctor says.
PALEOLITHIC DIET
Though this diet has been around since the mid-1980s, Loren Cordain, Ph.D., popularized it in 2010. The theory is that our modern diet, high in processed foods, dairy products and grains, is the main cause of obesity. To combat it effectively, Cordain said, people need to eat as their hunter-gatherer ancestors did. The diet puts no restrictions on lean meats, fruits or non-starchy vegetables (such as carrots or broccoli), and largely cuts out dairy, legumes, cereals and processed foods.
PROS: “Eating more whole foods and avoiding the heavily processed stuff is a great goal,” says Dr. Singh. This diet cuts out a lot of unnecessary sugar and carbs without upping the saturated fat in your system as keto does. It can also produce short-term weight loss, usually as a symptom of getting rid of carbs and sugary drinks in their entirety. Though this is a restrictive diet, there are more options than there are in keto and, as the doctor says, “It can be a great place to kick-start your health journey, and then you can slowly add back in the dairy and grains.”
CONS: The American Academy of Nutrition and Dietetics notes in a 2024 examination of the diet, “Should We Eat Like Our Caveman Ancestors?”, that its lack of whole grains is not ideal. Whole grains have been connected with a lowered risk of heart disease and some cancers. “Cutting out both grain and dairy also cuts out nutrients you need,” says Dr. Singh. “Dairy is the greatest source of calcium for most people.” He adds a practical point: “It’s also expensive to buy only whole foods all the time.”
MEDITERRANEAN DIET
One of the best-studied diets out there, this one prioritizes whole grains, legumes, fruits, vegetables, olive oil and fish, with allowances for alcohol, dairy products and meat. Most calorie intake comes from fish and plant-based foods.
PROS: This diet has been linked to a lower occurrence of cardiovascular disease. And not only has it been summarized as “nutritionally adequate for the general public” in a study published in Nutrients (“The Mediterranean Diet and Nutritional Adequacy: A Review”), but research has also shown its preventive potential for chronic diseases such as non-alcoholic fatty liver disease and breast cancer. In a 2024 study by Women’s Health Initiative, a Mediterranean diet was associated with a reduced risk of premature death in women. Because this diet does not heavily restrict food groups, it is less challenging to follow long-term.
CONS: People searching for an intensive immediate weight-loss solution may not find what they are looking for here, despite Mediterranean cuisine’s healthy rep. Also, if you’re worried about your iron levels, the lack of red meat may give you trouble unless you find compensatory sources.
RAW-FOOD VEGAN DIET
This diet plan takes veganism one step further. Besides cutting out meat, fish and other animal products, it also specifies that you eat only uncooked, unprocessed, plant-based foods such as fruits, vegetables, nuts, seeds and grains. Instead of traditional heating and cooking, raw food diets rely on juicing, dehydrating and blending as preparation methods. Some raw-food vegetarian (rather than vegan) diets allow the consumption of raw eggs and dairy, but this is less common because of food contamination concerns. This diet focuses on the health benefits of whole foods; its proponents consider even the application of heat to be removing foods from their most healthful state.
PROS: Plenty of benefits come with cutting red meat out of your diet. Too much red meat has been associated with heart disease, colorectal cancer and diabetes. In addition, processed meats, particularly processed chicken, have been associated with a higher risk of heart disease and type 2 diabetes. As noted above, cutting out carbs and high-fat processed foods will lead to short-term weight loss in many people. The raw-food diet is also naturally high in fiber, which is connected to a lowered risk of prostate cancer and certain gastrointestinal issues.
CONS: That fruits and vegetables are healthy is well proven; that they have a higher health benefit if eaten raw is highly debated. Dr. Singh adds that “with plant-based diets, there’s a danger of people not getting the right nutrients, vitamins and minerals, leading to deficiencies— and that can produce other health complications.” Meat and animal products are our bodies’ easiest source of things like zinc, iron, vitamin E, vitamin B12 and essential fatty acids. The raw-food diet is also low in calcium and highly restrictive—a red flag, our doctor says, for a plan you may not be able to stick to.
INTERMITTENT FASTING
Rising in popularity, this diet approach is all about the when rather than the what. Instead of calorie or food-group restriction, intermittent fasting focuses on scheduled eating and abstaining from food entirely for certain periods. Popular methods include alternate-day fasting, wherein you fast or restrict food every other day, and periodic fasting, wherein you eat normally within an eight-hour period and fast outside that time.
PROS: There is some evidence that intermittent fasting facilitates weight loss for certain people and populations. A review published in Canadian Family Physician (“Intermittent Fasting and Weight Loss: Systematic Review”) found that, on average, people lost 4.3 percent of their body weight practicing intermittent fasting for periods from two to 12 weeks. The National Institute on Aging also identifies this diet as more than a temporary weight-loss plan, noting that there is “interest in [its] potential health and aging benefits.” Our doctor says: “Yes, intermittent fasting can help some people, but you need to be careful with it.”
CONS: “Sometimes, people think, ‘Oh, this is my time to eat,’ and then they overdo it,” says Dr. Singh. “Or they’ll pick unhealthy foods. Also, this method isn’t good for a hectic schedule. What if there’s only one window in 16 hours when you can eat and you don’t have time to do so then? Then you’re not eating at all.” Lack of nutrition on fasting days can leave you sluggish, unfocused and irritable.
THE ATKINS DIET
Developed in the 1970s by the late cardiologist Robert Atkins, M.D., this diet seeks to correct a “metabolic imbalance resulting from carbohydrate consumption,” which he theorized was the main cause of obesity. It takes place over four phases, the first cutting carbs to under 20 grams a day for two weeks, and then slowly reintroducing them until reaching the “lifetime maintenance phase” in which a person is eating between 40 to 90 grams of carbs a day. Protein-rich foods are emphasized.
PROS: Cutting complex carbs from your diet will almost always result in a short-term shedding of “water weight,” as our expert has noted, and high-protein diets are known for being satiating and satisfying. In general, low-carb lifestyles combined with other “healthy” eating habits— keeping calories to the recommended number per day, stressing fruits and vegetables and limiting fat intake—have been shown to lower body weight across the board. A 2013 study published in the British Journal of Nutrition also showed a correlation between low-carb diets and lowered blood pressure.
CONS: Restricting carb intake to this degree is notoriously difficult, and Atkins has a high dropout rate. For example, one bagel is about 48 grams of carbs—almost all of your daily allowance in the lifetime maintenance phase. And dropping in and out of diets can have some serious consequences. “Many fad diets are hard to maintain very long-term,” says Dr. Singh. “If people are not able to stick with something, they start yo-yoing. They’ll lose weight and then gain it back, and every time they gain it back it becomes harder to lose it again. It’s frustrating, and it makes the whole process harder.”
WEIGHT WATCHERS
Designed to help you eat anything in moderation, Weight Watchers assigns “smart points” to different kinds of foods and then helps you track the number of points you eat in a day. Different diet plans offer different points goals. Some foods are zero points, such as fruits, vegetables and lean protein, meaning that these can be eaten at will. Portions of foods such as cheese, popcorn and salad dressing cost points, and that encourages you to eat smaller amounts of them.
PROS: One of Weight Watchers’s selling points is not “banning” any one food or food group. Having more options makes you more likely to stick to the plan, and therefore more apt to have long-term success. The Weight Watchers program also offers workshops and support groups for people on a weight-loss journey, and these, says our doctor, can make all the difference. “Programs like Weight Watchers, where other people help you keep you on track and give you a support system, can be very helpful,” Dr. Singh says.
CONS: You need to pay to have access to everything Weight Watchers has to offer, which is a huge barrier to entry for some. (Dr. Singh notes, however, that these expenses are sometimes covered by health insurance.) As with intermittent fasting, some who follow this plan feel the need to “stock up” on points so they can later overeat guilt-free, possibly with unhealthy foods, and that’s not ideal. Weight Watchers’s own health notices state that, though its program was created by dietitians, it isn’t for everyone. The plan should be avoided by those who are under age 18, pregnant or following an eating plan to treat a disease, whether that be diabetes or an eating disorder.
None of these diets is sheer fraud, but none is instant magic either. The point is to put knowledge, discipline and good sense together and, above all, be good to your body by choosing healthy foods. Talk to your doctor or healthcare professional before embarking on a major change in your eating, says Dr. Singh. And don’t celebrate victory or concede defeat too early—long-term improvement is what counts. Remember what the doc says: “The only diet that really works is the one you can stick to.”
