Low carb. Low fat. Paleo. Whole30. Mediterranean. Keto. These are just the tip of the iceberg when it comes to all the different diet plans you can follow. And, naturally, everyone's got an opinion on what's the best. Well, we're going to shatter everything you know (or think you know) about dieting: It doesn't matter what nutritionists and scientists say. It all depends on you, according to research from Newcastle University. Turns out, the "optimal" diet plan is called personalized nutrition.

The success of your diet relies entirely upon your body, mind, and attitude. But that's not to say you don't need help. In fact, the main takeaway from this new body of research is that people who receive personalized nutrition advice and support develop healthier eating habits—like eating less red meat and salt—and are more motivated to make necessary changes. The researchers also found using a website (available to you, too) is effective at influencing important lifestyle changes.

The science

In the study, published in the International Journal of Epidemiology, 1,607 adults from seven European countries were randomly assigned to four different groups.

One group was given conventional healthy eating advice, such as "eat at least five portions of fruits and vegetables daily" or "eat two portions of fish, one of which is oily fish, per week"; a second group received an individualized approach with advice and support based on an analysis of their current diet; a third group received personalized nutrition dependent upon their body fat percentage and blood markers; and a fourth group followed a nutrition plan based on their diet and genes (five genes with the strongest diet-gene relationship and opportunity to manipulate with diet were examined). Then, to help participants hone in on the aspects of their diets that needed the most help (or most change), each participant was given three personalized food-based goals. For example, you might be encouraged to choose whole grain varieties of bread and cereals to increase dietary fiber; or, you might be prompted to reduce or avoid certain high-fat dairy products to lower your intake of saturated fats.

Lastly, the three personalized nutrition groups joined the website Food4Me, an intervention study and forum on which experts survey the current knowledge of personalized nutrition and provide advice to volunteers (people looking to lose weight) to explore the application of individualized nutrition. The study subjects reported their dietary intake, eating patterns, and other relevant information for professionals to create optimized advice—all via the Web.

The takeaway

At the end of six months, 80% of the participants successfully completed the study and their diets, eating less red meat and more fruits and vegetables. Those randomized to the personalized nutrition treatment groups had significantly better and bigger improvements in their eating patterns; they experienced double the improvement when it came to the overall healthiness of their diets measured using the Healthy Eating Index compared to those in the control group.

What's more, the researchers found no evidence that personalization based on more complex information (like DNA and blood markers) made any difference to the outcome.

"What is exciting about this study is that we now know the Internet can be used to deliver personalized nutrition advice to large numbers of people," leady study author John Mathers said in a press release. "People find this approach convenient, and it is better at improving people's diets than the conventional one-size-fits-all approach. We would expect this to translate, eventually, to bigger improvements in health and well-being."

Now, we're not saying you have to join a research team or become a weight loss guinea pig. You can implement personalized nutrition on your own. Follow the tips from nutritionist Kristen Carlucci, R.D., below.

First, determine your goals

Cutting carbs may have helped your friend Joey cut fat, expose his abs, and expedite his bulk up. But, that's not necessarily the best plan of attack for you. For instance, if you're training for a marathon, you need "good" carbs to fuel your long runs. Think: "Are you looking to lose weight, put on lean muscle, maintain weight?" Carlucci says. All of these end games require pretty drastically different nutrition plans. Losing weight requires a calorie deficit (eat these but not these); lean muscle requires you eat more, but eat more of the right foods, namely protein (eat these); and if you're just trying to maintain weight, you need to doubledown on exercise and nutrition.

Factor in your workouts

"Nutritionally speaking, you'll still focus on high-quality foods (lean protein, fruits/vegetables, whole grains, healthy fats) in the diet whether you're performing a low- or high-intensity workout, but depending upon your goals, the calorie burn of your workout will effect how much you should be eating per day," Carlucci says.

If your goal is weight loss, you need to make sure you don't turn around after a workout and eat back everything you just burned. If you're slammed at work all week and don't make it to the gym even once, make sure you're not going over your daily allotment of calories each day (based on how many you burn at rest, with no exercise factored in). But if you're getting a mix of low-, moderate-, and high-intensity workouts in 5-6 times each week, you can eat a few hundred more calories than that baseline per day, says Carlucci. However, the number of extra calories should depend upon your goals: The guy bulking up is obviously going to need more than that. The guy trying to lean out may not add any extra calories even if he's working out most days of the week. Consider your goals and your training schedule.

Just to give you an example, a 165lb guy (who's 30 years old and 6' tall) would burn only 200 calories from doing one hour of low-intensity exercise (e.g., yoga), about 450 calories doing one hour of moderate exercise (e.g., swimming), and 630 calories doing one hour of high-intensity exercise (e.g., Crossfit), Carlucci says.

Pay attention to your hunger levels; you'll probably be much hungrier on a high-intensity workout day compared to a lower-intensity workout day. Make sure you're replenishing properly if needed—not teetering on either extreme of binging or starving yourself. "Men should never drop below 1,500 calories per day, otherwise you can do damage to your metabolism and slow your progress," Carlucci advises.

Factor in your lifestyle

You've probably heard a lot in the news lately about DNA-modeled nutrition plans. Considering whether you should take a test? "DNA-based insight is a really interesting and up-and-coming field," Carlucci says. "It may prove to be a very valuable tool, but right now it's still a new science that will take time to evolve; and while its approach is personalized, it's still unable to take into account specific lifestyle factors."

If you work 12-hour days and have a long commute, then a DNA-based plan saying you should be exercising for one hour a day, five days a week might be unrealistic for you. This is when creating your own personalized approach comes into play.

Maybe you set a goal to complete two one-hour workouts on Saturday and Sunday, plus two 20-minute high-intensity interval circuits during the work week. And you make an effort to make all (or nearly all) your meals at home and only eat out on Sunday or special occassions.

Think of your personality

"Will power and personality play a huge role when creating a personalized—and successful—nutrition plan," Carlucci says. You could save money and help fit healthier foods into your eating plan (as well as reduce temptation and cravings) by prepping all your meals in advance for the week. But if you're someone who can't stand leftovers or spending a ton of time in the kitchen, that won't be the best option for you. And odds are high you won't maintain it beyond a week.

You might be more successful if you set your goal to have 3-5 fast and simple weeknight meals you can easily prep when you get home (e.g., eggs with whole grain toast and fruit, or rotisserie chicken with one-minute brown rice, and a package of frozen vegetables).

Journal your food and physical activity

To illuminate your biggest challenges when it comes to healthy eating, journal for a week. Maybe you drink a few too many beers during the week, skip breakfast, or overeat late at night because you don't have healthy meals or snacks at work. "Take three of these challenges and set specific goals around each of them them," Carlucci suggests. "For example, if you're currently having at least 15 alcohol-based drinks per week, you could make a goal to set a drink limit of 7-10 drinks per week." This way you're not overwhelming yourself with too many "to-do's". When these new goals become habitual, focus on three new goals until you eventually create permanent lifestyle changes.