popular diets foods | why crash diets don't work
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This article discusses diet culture, restrictive eating patterns, and disordered eating.

Key points

  • The long-term effectiveness of restrictive diets like keto, Paleo, and counting calories doesn’t have a lot of scientific support. In fact, research suggests they often backfire. 
  • Restrictive diets can sometimes lead to disordered eating. 
  • Intuitive, or mindful, eating is a healthier, proven form of healthy weight management.

Ketogenic or very-low-carb diets

Think of the ketogenic diet (or “keto” for short) as a super-extreme version of cutting carbohydrates (aka “carbs”)—from whole grains, fruits, and veggies to pasta, white bread, and baked goods. According to this food philosophy, you can have little to no glucose or carbohydrates—not even the whole-food varieties, which your brain and body need to perform.

Typically, a keto diet starts with a three- to four-day period of fasting in which you either forgo food entirely (which can be dangerous—especially when you’re not under the supervision of a doctor) or cut out all carbs, which will kick your body into a state of ketosis, where your body starts burning fat instead of carbs. “Your brain’s preferred food is glucose, so when there’s not enough [in your body], that triggers the production of ketone bodies from fat as a kind of backup fuel,” says Jenna Heller, a registered dietitian at Arizona State University. The idea is that instead of using carbs for energy, your body starts burning fat for fuel. After that, dieters eat a high-fat diet, getting about 75 percent of their calories from fatty foods, 20 percent from protein, and the rest from the occasional, limited source of carbohydrates.

  • Kicking your body into a state where it exclusively burns fat promises dieters a rapid, significant reduction of fat.
  • Research is limited and somewhat controversial, but in an opinion piece published in the Journal of Nutrition, Dr. David Ludwig suggested that a ketogenic diet may potentially be helpful in treating type 2 diabetes.
  • Taking low-carb eating to the extreme—like any extreme diet—is an unsustainable way to maintain health over the long term.
  • Cutting carbs also means unnecessarily missing out on nutrient-dense foods like fruits, veggies, and whole grains.
  • Several studies suggest that following a keto diet can actually damage the body in the long term. The European Society of Cardiology announced findings in 2018 that following a very low-carb diet can increase your risk of dying of heart disease or cancer.

“I would never propose that someone go on this and stay on this,” says Tammy Ostroski, doctor of nursing and manager of the health clinic at Arizona State University.

Paleo Diet

The idea behind the Paleolithic (or “Paleo”) diet is to eat like your ancestors—as in the hunter-gatherer kind. The premise is that modern, processed foods are inferior to the simpler, more natural diets of ancient humans (which recent research has in fact found to be mostly plant-based). The Paleo diet says you can only eat grass-fed meat, fish, fresh fruits and veggies, eggs, certain nuts and seeds, and so-called “healthy” oils (such as olive or avocado). What isn’t allowed on your plate? Whole grains, legumes (e.g., peanuts, lentils, peas, and beans), dairy, sugar, processed foods, and salt. 

  • Adopting a caveman-style cuisine will guide you toward more nutritious choices while keeping you away from processed foods, sodium, high-glycemic foods, and “unhealthy” oils (which Paleo practitioners define as more processed and having a less-than-ideal fatty acid ratio).
  • Proponents claim the Paleo diet will help prevent blood sugar spikes, and boost heart and kidney health.
  • The Paleo diet tends to be high in saturated fats, which have been linked to a higher risk for heart disease, according to the National Institutes of Health.
  • The evidence for Paleo is iffy. While several studies suggest that following a Paleo diet can reduce waist size and weight, lower “bad” LDL cholesterol levels, and increase insulin sensitivity, many of these studies have small sample sizes (think 30 people or less), lack a control group (i.e., there’s no other group to compare results to), and are short term (a few weeks to a few months), according to a 2016 review of the evidence published in Australian Family Physician. 
  • The limited long-term evidence isn’t promising—after just two years, initial improvements in waist circumference and body fat percentage weren’t maintained over time, according to a study published in the European Journal of Clinical Nutrition.

“This ‘natural is better’ focus is really common in diets in recent years,” says Heller. “When we look at the science, and what we know about what’s best for the human body, that’s not always reflected in what our ancestors did.” Case in point: Paleo-style eating often causes you to unnecessarily eliminate nutritious foods like whole grains, says Heller.

Plus, the Paleo diet can be quite expensive to keep up with—budget-conscious students shouldn’t have to shy away from low-cost, nutrient-dense food options, like something made with a forbidden legume (e.g., peanut butter), just to stick to Paleo rules.

If It Fits Your Macros

The idea behind the “If It Fits Your Macros” diet is pretty simple: You can eat whatever you want as long as you get the right balance of macronutrients (carbs, protein, and fat) and hit your daily calorie allotment. Typically, recommendations are around 40–50 percent of calories from complex carbs, 30–40 percent of calories from protein, and the rest from healthy fats. Simple in concept? Sure. But when it comes to actually making meals? Not so much.

  • This diet plan claims to work with your goals (either losing weight, gaining muscle, or both) without ruling out any specific foods—in other words, you can still eat the pasta and pizza as long as it fits within your macro goals.
  • “Where macros go wrong is that there’s a weird emphasis on manipulating calories,” says Heller. This diet requires you to track everything you eat and drink throughout the day, count calories from each nutrient, and measure and weigh all your food. 
  • Because you have to stay on top of measuring and counting, that often means bringing your own precooked and measured food everywhere. Not exactly fun (or sustainable).

“For many people, this level of detail and tracking isn’t sustainable and doesn’t work long term,” says Alissa Rumsey, a registered dietitian in New York. “Some people run the risk of developing disordered eating behaviors from being hyper-focused on counting nutrients and measuring food all the time.”

Calorie Restricting Diets

Counting your calories is one of the oldest and most persistent diet trends around. Again, the premise is simple: What you eat doesn’t matter as long as you restrict your total calorie intake.

  • Cutting calories has long been touted as a way to achieve and/or maintain a certain weight and doesn’t place any importance on what you’re eating, making it super flexible. 
  • When researchers studied participants following diets that emphasized different ratios of protein, fat, and carbohydrate, they found that the ratio of what foods they ate didn’t ultimately matter for weight loss. The only predictor of how much weight they lost was how many calories they ate overall, according to the findings published in the New England Journal of Medicine.
  • Low-calorie diets can lead to unhealthy eating behaviors. Theoretically, you can stay within the rules of the low-calorie diet by eating nothing but 100-calorie cookie packs—but that doesn’t mean you’ll be getting any of the nutrients you need.
  • “Lowering calories too far below what your body needs can cause muscle loss—which is very bad for long-term weight maintenance—and [can] damage your metabolism,” says Rumsey. 

Cutting calories isn’t sustainable. In fact, this statement sums up what science has to say about “diets” in general—they don’t work for fueling your body toward better health in the long run. 

Why crash diets fail

Biological changes

When researchers followed up with competitors on a popular weight-loss show six years after they’d dieted to the extreme, they found the participants had gained most of the weight back (and that their transformations had actually caused major metabolism slowdowns that persisted for years), according to the study published in the journal Obesity. This isn’t a new phenomenon, either—metabolic changes after weight loss are likely one of the reasons it’s so hard to keep the pounds off long term, according to a meta-analysis in the American Journal of Clinical Nutrition.

Risk of long-term restriction

The more restrictive the diet, the harder it is to keep up and the more you run the risk of getting into dangerous restrictive-eating territory, says Ostroski. “The thing that concerns me is that students start thinking, ‘I can’t eat this, I can’t eat that,’ and then they tend to binge—it becomes a negative feedback loop.”

“I counted/restricted calories and counted macros for about two years. I had a binge eating disorder and was obsessed with body image. I stopped because it was affecting my mental health. Once I stopped and focused more on sleeping and mental health, I actually lost a lot of weight and my eating habits normalized.”
—Sabrina S., first-year graduate student, Utah State University, Logan

OK, we get it: Diets don’t work. So now what?

What does work, according to science, is focusing more on your mindset than what you’re munching on—a strategy called intuitive eating

Remember, eating healthfully isn’t a one-size-fits-all plan—if you’re an athlete on the sports team, your nutritional needs will be different than those of some of your classmates, and vice versa. If you’re not sure how to eat best for your body or are struggling with your relationship with food, talk to an expert. Reach out to your health care provider, an on-campus nutritionist or registered dietitian (most schools provide these services through the health center, dining services, or athletic programs), or an intuitive eating counselor to talk about the eating habits that best suit your individual needs.

If you or someone you know may be struggling with disordered eating behaviors or body dysmorphia, find help and resources by visiting the National Eating Disorders Association.

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Article sources

Jenna Heller, MS, registered dietitian, Arizona State University.

Tammy Ostroski, DNP, FNP, manager of health clinics, Arizona State University.

Alissa Rumsey, MS, registered dietitian, New York.

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