Keto, Paleo, Mediterranean, pescatarian, flexitarian, beer and bread (okay, I made up that last one) – but you get the idea. It seems like every so often a new fad diet pops up, and we all have one friend who swears by it.

Although there is no argument that a healthy diet benefits our overall health, what is right for some individuals isn’t right for others. To sort it all out, here is a short guide to shed light on today’s most popular diets and who might benefit from following them.  

Keto

The short answer: A high fat, low-carb diet. 

The long answer: The keto – or ketogenic diet – is one of the most talked about diets in recent years. Its goal is to get an individual’s body to attain “ketosis,” a metabolic state caused by the drastic reduction of carbohydrates in the diet.

With a drastic reduction in  carbs, the body begins to use fats as its main energy source. The body breaks down fats in the liver, which produces ketones, a type of acid, which then replace glucose as the primary source of energy. Although a ketogenic diet comes in different forms, it typically involves 70-75 percent of an individual’s calories from fats, 20 percent from protein, and only 5 percent from carbs.

Who it is for: This strict, but tasty dietary plan has been used as a treatment option for epilepsy for more than a century, and in the past few decades as a dietary plan for individuals who have metabolic syndrome or type 2 diabetes. More recently, it has become a popular choice for endurance athletes and for overweight individuals looking to manage their weight.1

For athletes, one study found that compared to a high-carbohydrate diet group, 12 weeks of a ketogenic diet plus high intensity-interval training and endurance and strength exercises, led to enhanced body composition, fat oxidation during exercise, and specific measures of performance relevant to competitive endurance athletes.2

Key foods to eat: Almost any food that does not contain carbohydrates and is high in fats, such as fish and natural meats like beef, pork, and poultry. Eggs, full-fat dairy products, nuts and seeds, and low-sugar fruits, like berries or coconut, are also good options. 

Key foods to avoid: Avoid all high-sugar fruits and juices, starchy vegetables, grains, legumes, and sugar-based sweeteners. Alcohol should also be avoided. 

Paleo

The short answer: Eat like a hunter-gatherer

The long answer: Paleo, a popular recent diet, gets its name from the Paleolithic era; the core concept is to eat like an early human from that era, avoiding processed and even farmed foods, and only eating foods that could be obtained by hunting and gathering. This means avoiding processed foods, sugar, dairy, and grains, and incorporating primarily meats, seeds, nuts, and certain fruits and vegetables. Keep in mind this is a general description; there are modified versions that allow certain grains, pseudograins, or dairy.

Who it is for:  Avoiding processed food is generally a good guideline for everyone, so those looking to maintain a healthy weight could potentially benefit from following this diet. However, it is important to note there are very few long-term clinical studies about the benefits/risks of the paleo diet.

Key foods to eat: Meat, fish, eggs, vegetables, nuts, seeds, and healthy fats 

Key foods to avoid: Grains, breads, legumes, dairy, potatoes, and all artificially processed foods 

Gluten-free

Short answer: The name says it all – goodbye gluten!  

The long answer: You are probably familiar with the term gluten-free. Following a gluten-free diet simply means excluding gluten – a protein commonly found in wheat barley, rye, and other grains – from your diet.

Who it is for: There are two reasons to consider a gluten-free diet. One, a person is gluten intolerant, or two, a person has celiac disease. Both are reasons why an individual would remove gluten from their diet.

Gluten intolerance causes gas, bloating, cramping, diarrhea, and constipation. Gluten intolerance also results in symptoms outside the GI tract, such as skin rashes, headaches, fatigue, moodiness, and muscle cramps. Celiac disease (CD) is not the same as gluten intolerance. CD is an autoimmune disorder in which gluten can cause serious, even life-threatening, complications when it attacks the cells of the small intestine.

In CD, even the tiniest bit of ingested gluten can cause inflammation and damage to the intestinal wall. CD is typically diagnosed with a biopsy in the small intestine.

Key foods to eat: Any naturally gluten-free foods, or gluten-free alternative grains and flours, such as cornmeal, buckwheat, quinoa, or soy.

Key foods to avoid: Anything containing gluten

Low-FODMAP

Short Answer: Avoiding fermentable carbs

The long answer: This diet involves cutting out groups of fermentable carbohydrates that can cause GI distress in certain individuals. Fermentable carbohydrates are carbohydrates that are only partially absorbed into the bloodstream, which means the remainder must be digested (or fermented) by your gut microbiome.

When the microbes in your microbiome digest FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols), gases are given off, which can cause gas, bloating, and discomfort. In addition, FODMAPs in the gut draw in water, which further results in pain, cramping, and diarrhea.

Who it is for: The low-FODMAP diet was developed by researchers at Monash University in Australia who were looking for dietary answers to IBS. Despite being very beneficial, a low-FODMAP diet can be hard to follow because it restricts so many common foods, as well as many foods we think of as being healthy.

Key foods to eat: Foods naturally low in FODMAPs. Learn more about the Low-FODMAP Diet here.

Key foods to avoid: Foods high in FODMAPs, such as onions, garlic, asparagus, avocados, bananas, watermelon, sausage, and any foods made with wheat, milk, yogurt, honey, or fruit juice.

Mediterranean / Modified Mediterranean

The short answer: Eat like the Greeks

The long answer: The Mediterranean Diet gets its name from how individuals eat in the region surrounding the Mediterranean Sea. Although there is no single definition, the diet focuses on daily consumption of vegetables, fruits, whole grains, and healthy fats, with the occasional addition of fish and poultry throughout the week.

There is also Thorne’s Modified Mediterranean Diet, which goes a step further by removing common allergens, such as gluten, that can contribute to inflammation and weight gain.

Who it is for: The Mediterranean Diet is commonly recognized as promoting good cardiovascular health, so it is a good choice for individuals interested in maintaining heart health. There is also credible research that shows the Mediterranean Diet protects against diseases such as metabolic syndrome, diabetes, cancer, inflammatory bowel disease, cognitive dysfunction, and arthritis – all chronic conditions associated with inflammation.

Key foods to eat: Large amounts of fresh vegetables and moderate amounts of fruit, in addition to whole grains, beans, nuts, and seeds. Fish, and to a lesser extent lean meat and poultry, are eaten in moderation. Fresh fruit is the typical daily dessert and olive oil is the primary source of fat.

Key foods to avoid: Fried foods, hydrogenated oils, refined carbohydrates (baked goods from refined flour and sugary desserts), beverages with added sweeteners (sodas and juices), high-fructose corn syrup, and fatty, processed meats, such as lunch meat, bologna, and ham.

Plant-based diets

The short answer: Vegans, vegetarians, pescatarians, and flexitarians

The long answer: These diets are primarily plant-based, with key differences being how they view animal products. On one end of the spectrum is the vegan diet, in which all foods from animals are prohibited, including eggs, cheese, and honey.

Vegetarians, to some degree, allow certain animal products, including:

  • Lacto-ovo (or ovo-lacto): allows eggs and dairy, but no meat, poultry, or seafood
  • Lacto vegetarian: allows dairy only, but no eggs, meat, poultry, or seafood
  • Ovo vegetarian: allows eggs only, but no dairy, meat, poultry, or seafood
  • Pescatarian: plant-based diet, which adds fish and other seafood, but no poultry or meat

On the other end of the spectrum is the flexitarian. Although they don’t technically meet traditional definitions of vegetarianism, individuals who follow this diet strive to avoid meat, poultry, and seafood when possible, but don’t completely abstain from animal products.

Who it is for: Individuals who follow these diets do so for health or ethical reasons. Because these diets, to a degree, share similarities with the Mediterranean diet, they share some similar health benefits. However, it is important to keep in mind that vegetarians and vegans should be aware of possible nutrient gaps in their diet. Here are some additional tips for followers of a plant-based diet, to ensure you get the nutrients you need to function at your best.

Key foods to eat: The main food groups are vegetables, fruits, whole grains, and protein sources such as beans, nuts, and seeds. 

Key foods to avoid: Varies, but includes avoiding animal-based food groups.  

Before starting any new diet 

There are multiple reasons to choose a new diet, including certain health reasons, weight management, improving athletic performance, or ethical convictions. Whatever the reason, it is important to consult with your health-care provider before embarking on a new diet, to help you modify your diet based on your health goals and past health concerns.

References

  1. Bueno N, De Melo I, De Oliveira S, Da Rocha Ataide T. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: A meta-analysis of randomised controlled trials. British Journal of Nutrition 2013;110(7):1178-1187. doi:10.1017/S0007114513000548
  2. McSwiney F, Wardrop B, Hyde P, et al. Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes. Metabolism 2018;81:25-34.