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When it comes to making healthy food choices, it can be hard to know which way is up. Trendy diets that sound way too weird or way too hard, healthy eating tips that contradict each other, and a lack of long-term research can make it difficult to determine what’s actually a healthy choice.

In the traditional sense, all “diets” (as in short-lived, regulated eating plans, not your nutritional intake in general) have a couple major things in common: rules about what you can and can’t eat, and guidelines about how much you’re allowed to munch. While some diet trends come and go (juicing, the South Beach diet, the cabbage soup diet?), others have more staying power. Let’s take a look at what’s out there now, dive into what the evidence says (or doesn’t say), and get some real-life, research-backed tips for making healthy eating less confusing and more convenient.

Before we get going, let’s clear the air—check with your doctor before making any drastic changes to what and how you’re eating. What you eat depends on your individual needs, and your doc can help figure out what works best for you.

Paleo-based dietsAsian male food shopping for vegetables

The rules

The idea behind this 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 means you can only eat grass-fed meat, fish, fresh fruits and veggies, eggs, certain nuts and seeds, and 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. (Potatoes are up for debate at the moment, but we know one thing for sure: Sweet potatoes are in.)

The promises

According to paleo proponents, adopting a caveman-style of cuisine will guide you toward healthier choices while keeping you away from unhealthy oils, sodium, and high-glycemic foods (i.e., foods that cause a blood sugar spike, which is associated with an increased risk of some cancers, type 2 diabetes, and heart disease). They assert that following this diet will help prevent blood sugar spikes, and boost heart and kidney health.

The problems

While most nutritionists are totally behind keeping processed foods to a minimum, Stone Age snacking has a lot of caveats. (For one, 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.)

“This ‘natural is better’ focus is really common in diets in recent years,” says Jenna Heller, a registered dietitian at Arizona State University. “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 healthy foods like whole grains, says Heller.

The evidence for paleo is iffy. While several studies suggest that following a paleo diet can reduce waist size and weight, lower bad 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 2014 study published in the European Journal of Clinical Nutrition.

Finally, Heller also warns the paleo diet can be quite expensive to keep up with—students shouldn’t have to shy away from low-cost, healthy food options like something made with a forbidden legume (e.g., peanut butter) just to stick to paleo rules.

Ketogenic or very-low-carb diets
Female following recipe on tablet

The rules

Think of the ketogenic diet (or ketosis diet) as a super-extreme version of cutting carbs, which include less healthy things (e.g., white pasta, white bread, and baked goods) and healthier things (e.g., whole grains, fruits, and veggies). According to this food philosophy, you can have little to no glucose or carbohydrates—not even the healthy ones.

Typically, it starts with a three- to four-day period of fasting in which you forgo food entirely (hangry much?) 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 Heller. In other words, 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 carb.

The promises

Kicking your body into a state where it exclusively burns fat promises dieters a rapid, significant reduction of fat.

The problems

According to the long-term evidence, taking low-carb eating to the extreme isn’t part of maintaining a healthy weight over time. Participants with type 2 diabetes who tried the low-carb lifestyle for a two-year period initially showed improvements in health—reduced weight and improved glycemic control, according to a 2012 study published in the journal Diabetologia. But compliance with the diet dropped off after six months—and so did the weight change, which the authors thought was likely because the restrictions were too hard to stick to in the long run. “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.

Like with paleo, cutting out carbs to the extreme also means unnecessarily cutting healthful foods like fruits, veggies, and whole grains. And the risks associated with taking in high amounts of saturated fat are there too, just like with paleo.

Counting macrosClose up of hands chopping vegetables

The rules

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.

The promises

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.

The problems

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

Because you have to stay on top of measuring and counting, that often means bringing your own precooked and measured food when you go out to dinner with friends or have snacks with your study group. Not exactly fun (or sustainable).

Finally, the lack of emphasis on which foods you can and can’t eat can also be detrimental to your health. “Many people who count macros use a numbers-only approach at the expense of nutrition,” says Rumsey. “For example, you can get 40 grams of carbs in the form of a cup of quinoa, or you could get it from 16 Sour Patch Kids. While you’ll ‘hit your macros’ either way, each will have a very different effect on your insulin response, satiety, and energy level.”

Low-calorie dietsYoung woman eating and writing

The rules

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

The promises

Cutting calories has long been touted as a way to maintain a healthy 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.

The problems

Technically, this diet does what it says—reducing your calorie intake will likely make the number on the scale go down. But proponents leave out three incredibly important details.

First, like many diets, it can be unhealthy in other ways. 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.

More importantly, going too low can cause major long-term problems, says Rumsey. “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.”

And finally, it 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. Here’s why:

  • Less enjoyment “Diets deprive us both physically and psychologically of things we tend to really like. When you limit yourself from something that you really like, it actually comes back to bite you in the long run,” says Dr. Brian Wansink, director of the Cornell University Food and Brand Lab in New York and author of the books Mindless Eating (Bantam, 2010) and Slim by Design (William Morrow, 2014). “As a result, diets tend to be very unsustainable.”
  • 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 they’d 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 post 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.”

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

What does work, according to science, is changing your habits and focusing more on your mindset than what you’re munching on. The idea is to “change the convenience, the attractiveness, and how normal it is to eat [healthy] foods,” says Dr. Wansink.

To learn simple strategies for eating better without going on a diet, check out How to eat what you love & love what you eat.

Remember, eating healthy isn’t always one-size-fits-all—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 bod or are struggling with your relationship with food, talk to an expert. Reach out to your health care provider or an on-campus nutritionist (most schools provide those services through the health center, dining services, or athletic program) to talk about the eating habits that are healthiest for you.

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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.

Brian Wansink, PhD, director of Cornell University Food and Brand Lab, Cornell University, New York.

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