Different Diets, What They Entail, and Potential Impacts

Medically reviewed by Dr. Stacy Hengisman MD and Felice Ramallo MSRD.

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What is the best diet plan for weight loss? Sometimes it feels like the number of diets available are so numerous it’s difficult to keep track. From paleo, to keto, to gluten-free, most of us only know what a handful of these terms typically mean, nevermind whether they’re health conscious, nutritious, or even accessible to regular people who visit their neighborhood Walmart, Albertsons, or Trader Joe’s a couple of times a week. So let’s talk about about the most popular diets today, their general ‘guidelines’ (we intentionally don’t use the word ‘rules’, since a diet should not prescribe you rules: the only rules are what you decide is right, for your body), and what the research says concerning the potential upside effects of following these diets.

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It’s also worth pointing out our definition of the word ‘diet’. For the purposes of this article, we’ll be talking about the most popular diets and their evidence-based health results for certain conditions, making sure to evaluate how sustainable they are for their followers over a long period of time, and what a typical day consuming this diet might look like.

Explaining the most popular diets

Mediterranean diet

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Background on this diet:

This diet is thought to be based around the foods that living in countries surrounding the Mediterranean Sea have traditionally consumed - think North African countries, Spain, Greece, and Italy.

What this diet entails:

The Mediterranean diet generally encourages more vegetables, fruits, plant-based proteins, seafood, grains, nuts, seeds, and antioxidant-rich fats, such as olive oil. It also allows dairy and meat, though in smaller quantities than the typical American diet. Though this diet doesn’t veto sweets (in fact, homemade and regional pastries, fruit salads, dates, olive oil cake, and Greek yogurt with honey are all popular sweet treats for those living in these countries), this diet does generally discourage the overconsumption of processed foods and added sugars.
A “Mediterranean Diet” is not really about the region that it’s from. It’s about having a plant-forward diet with lots of produce, nutrient-rich proteins, whole grain or vegetable starches, and healthy fats.

Example dishes:

Breakfast:

Greek yogurt with granola and strawberries on the side
Whole grain cornetto (or any other whole grain bread), deli meat slices (think sliced turkey, roast beef, etc.), whole milk cheese, and a fruit salad
Cold cereals or muesli with milk, sliced nuts, milk, fresh berries
Shakshuka with eggs, whole grain pita, topped with fresh herbs

Lunch:

Grilled local fish salad with ancient grain pasta and asparagus in lemon and olive oil
Bean and pasta soup (pasta e fagioli) with a side salad
Grain and vegetable salads (bulgur, farro, millet) with roasted herb chicken

Snacks:

Cottage cheese with local fruit
Yogurt with oat granola and berries
Fresh vegetables, hummus, whole grain pita

Dinner:

White wine steamed mussels with crusty whole grain bread drizzled in olive oil with a side veggie
Grilled fish with ancient grain pasta and a sliced fennel salad
Steamed artichokes with stewed chicken over a cooked grain or pasta

Potential health impacts:

Several studies have indicated that the Mediterranean diet can help with:

Helping to prevent heart attacks
Reducing risk of stroke and type 2 diabetes

All these potential benefits are thought to be the result of a couple of consequences of this sort of diet:

Slowed progression of plaque build up (a major risk of heart disease)
Reduced fasting blood sugar levels and stabilized blood sugar generally
The body’s improved “ability to regulate blood sugar levels effectively,” which has been shown to decrease insulin resistance (a precursor to type 2 diabetes)

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Paleo diet

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Background on this diet:

Upon first glance, paleo has some overlap with the Mediterranean diet - they both avoid processed foods. Paleo goes one step further in that it is designed “to resemble what hunter-gatherer ancestors ate thousands of years ago,” with a focus on whole foods. As a general rule of thumb, this means foods that have not been processed through a factory - instead, they come ‘out the ground’ (think vegetables, fruit, and seeds, which were foraged), or they are sources that ancestors would hunt themselves (fish and meat).

What this diet entails:

Staples of the paleo diet include vegetables, fruits, seeds, herbs, spices, fish, meat, and eggs.

Example dishes

Breakfast:

Scrambled eggs with avocado on the side and turkey sausage

Lunch:

Cobb salad (generally without the blue cheese)

Snacks:

Chia seed pudding
Banana with almond butter (peanuts are a legume so peanut butter is avoided on a Paleo diet)

Dinner:

Steak with asparagus spears, mushrooms, and kale

Potential health impacts:

Harvard Health reports a couple of studies have shown that the Paleo diet, over the short term, may be linked to “greater weight loss, reduced waist circumference, decreased blood pressure, increased insulin sensitivity, and improved cholesterol” - however, these studies were conducted on a small number of participants, and were of a short time period (6 months or less), meaning that much more research is needed to understand how effective the Paleo diet is over a long period of time.
Interestingly, one long-term study of 24 months that followed 70 post-menopausal women in Sweden with obesity, found that compared to the ‘Nordic Nutrition Recommendations’ (NRR) diet, the group following the Paleo diet “produced greater fat loss at 6 months but not at 24 months” and that triglyceride levels were lower at both the 6 month and 24 month mark. This would be a potential positive effect since a high level of triglycerides is thought to contribute to hardening of the arteries and related to a higher risk of stroke or heart disease.
It’s also important to point out that this diet could put you at risk of deficiency for calcium and vitamin D (important for bone health), while the amount of meat some people might rely on consuming in this diet to fit into the ‘paleo’ category means “you may consume saturated fat and protein far above recommended levels due to eating so much meat” which “can cause an increased risk of kidney and heart disease and certain cancers,” according to an article published by UC Davis Health.

Keto diet

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Background on this diet:

The Keto diet is a low-carb, high-fat diet that “aims to force your body into using a different type of fuel,” so that instead of relying on glucose which comes from carbs, your body is forced to rely on ketones, “a type of fuel that the liver produces from stored fat.”

What this diet entails:

This diet has a high emphasis on fatty fish, meat, eggs, dairy products, and low-carb vegetables (such as onions and tomatoes) while drastically reducing the number of carbs you consume. Harvard Health does a good job summarizing the level of carbs consumed on this diet when it contextualizes the following: some Keto variations typically recommend a guidance amount of 20g to 50g of carbs per day; this is a tiny amount of carbohydrate to consume, since a medium-sized banana on its own consists of about 27g of carbs.
It’s important to point out that there are different variations of the Keto diet - the Standard one (SKD) typically breaks down to 70% fat, 20% protein, and 10% carbs. There is also the Cyclical diet (5 ketogenic days to 2 high carb days), and the Targeted diet (adding carbs around workouts), as well as the High-Protein diet

Example dishes:

Breakfast:

Tomato and onion omelet

Lunch:

Bunless burger with avocado and cheese on top, as well as spinach on the side

Snacks:

Hard-boiled eggs
A cup of full-fat Greek yogurt with Walnuts on the side

Dinner:

Grilled salmon in butter, with cheese topped cauliflower florets and mushrooms

Potential health impacts:

The Keto diet has also been linked to weight loss, but it also carries with it several risks. Of high importance is the diet’s emphasis on consuming animal products which are high in saturated fats.

Saturated fats (those found in meat and dairy), versus unsaturated fats (think olive oil and avocados), are often linked to ‘bad’ - LDL - cholesterol in the blood and its association with heart disease risk.

One review published in the Journal of the Endocrine Society also points out that “more information is needed on long-term complications of the ketogenic diet on glucose homeostasis in the body as well as in the brain” - they reference several case reports and case series of “individuals developing hypoglycemia due to the ketogenic diet, with most of those reported in children.”
Studies carried out which monitor the impact of a Keto diet have demonstrated it can lead to weight loss, but problematically, most of these have been “short-term” and with “mixed results.” Therefore, the long-term implications of following the Keto diet have yet to be thoroughly understood and explored. Because of the low carbohydrate focus this diet promotes, it should certainly only be considered in collaboration with your doctor and a registered dietitian.

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Plant-based diet

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Background on this diet:

A plant-based diet can be as strict as a vegan diet, or as flexible as the Mediterranean diet (with the idea that you’re still eating a small amount of fish, dairy, and meat, but the majority of your choices are derived from plant-sources). In its best form, this diet focuses mainly on consuming vegetables, fruits, legumes, beans, nuts, whole grains, oils, and seeds, and this variation of it can sometimes be referred to as a whole-foods, plant-based diet (WFPB ).

What this diet entails:

A plant-based diet centers around reducing one’s intake of processed foods, in addition to lowering the amount of meat, and sometimes dairy, consumed as well. Most recipes will have the majority of the plate filled with rice, beans, produce (fruits or vegetables), and if there is meat, it is likely in a smaller amount or less frequently that the typical American plate contains.
This often goes along with increasing potentially higher-quality foods - such as organic foods (which exclude the use of antibiotics and added growth hormones in farm livestock) - although of course since organic selections are typically more expensive, you do not have to eat organic to eat a WFPB diet, by any means!

Example dishes:

Breakfast:

Scrambled tofu with sweet potato and black beans
Avocado mashed with white beans on sourdough toast
Oatmeal with nuts, seeds, and fruit

Lunch:

Vegetable tempeh stir fry with black rice
Veggie wrap with marinated seitan or cheese
Leafy green salad with roasted chickpeas and vinaigrette

Snacks:

Chia seed pudding with oat milk and tropical fruit
Apples and nut butter
Sliced veggies with hummus or another dip

Dinner:

Paneer and red pepper curry with brown basmati rice
Bean-based veggie burger on a whole grain bun with a side of root vegetable fries
Ramen with sliced vegetables and crispy tofu

Potential health impacts:

One review reported that “there is a general consensus that the elements of a whole-foods plant-based diet - legumes, whole grains, fruits, vegetables, and nuts, with limited or no intake of refined foods and animal products - are highly beneficial for preventing and treating type 2 diabetes”

The authors conjecture multiple potential reasons for why one’s chances of insulin resistance might be lowered on this type of diet, including:

Increases in fiber
Increases in phytonutrients
Food-microbiome interactions
Decreases in saturated fats
Heme iron
Promotion of a healthy body weight

A WFPB has been linked to reduced risk of heart disease, a reduced risk of certain types of cancers (colorectal and gastrointestinal cancer), and a lower risk of cognitive decline and Alzheimer’s disease. The caveat here is that not all diets lowering animal product consumption are created equal: evidence suggests that “unhealthy plant-based diets that included sugary drinks, fruit juices, and refined grains were associated with a slightly increased risk of heart disease.”

Gluten-free diet

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Background on this diet:

Gluten is a family of proteins found in many wheat and some grain products; therefore, a gluten-free diet is one that excludes gluten - this can be through either foregoing foods that have gluten in them, or choosing gluten-free options. Harvard Health reports, though, that “there is no compelling evidence that a gluten-free diet will improve health or prevent disease if you don’t have celiac disease and can eat gluten without trouble.” So unless you have a wheat allergy, non-celiac gluten sensitivity (shortened to NCGS), celiac disease, or you suspect you may have one of the conditions above, Harvard Health points out there is no scientific evidence promoting the idea of quitting gluten if you can tolerate it just fine. For the people who do have trouble digesting gluten, they can have uncomfortable or painful (in the case of a wheat allergy - life endangering) symptoms that arise after consuming gluten, and for them, gluten is something to be avoided.

What this diet entails:

Since this diet entails cutting out gluten, many people consume rice, corn, potatoes, and other starchy veggies (gluten-free options) as replacements for foods that typically contain the protein. Foods to be avoided on a gluten-free diet generally include: many cereals, pasta, wheat-based bread, baked goods made from wheat flour, and any other ingredient derived from wheat, rye, spelt, or barley. (The exception to this is those with a wheat allergy - they should avoid wheat, but can eat barley and rye). Gluten-free options may also be a path to explore if you still want to consume popular staples like pasta and bread.

Example dishes:

Breakfast:

Gluten-free English muffins with veggie scrambled eggs
Corn grits with eggs and salsa
Buckwheat waffles with maple tahini butter and berries

Lunch:

Caesar salad with chicken -hold the croutons and pick another gluten-free starch instead
Sorghum grain bowl w/ protein and veggies
Loaded sweet potato with black beans, bell pepper, avocado, fajita veggies, cheese

Snacks:

Banana-peanut butter protein smoothie
Berries with cottage cheese
Gluten free crackers with cheese and sliced apple

Dinner:

Mexican burrito bowl (white or brown rice, black beans, guacamole, beef, sour cream, and pico de gallo)
Thai red curry with stir-fry veggies and shrimp over quinoa
Grilled protein, roasted carrots, and mashed potatoes

Potential health impacts:

For those with celiac disease or NCGS, avoiding gluten delivers benefits in the way of not experiencing troubling physical symptoms that can inhibit one’s quality of life. Apart from that, there isn’t evidence to suggest that for those who digest gluten just fine, that excluding gluten would be beneficial.
In fact, if you don’t have a gluten intolerance or celiac disease and you decide to cut out foods with gluten in them, Johns Hopkins Medicine warns there is a risk that you lose access to foods that hold nutritional value in the form of fiber, vitamins, and micronutrients. Indeed, “getting enough whole grains in your diet is especially important if you’re at risk for heart disease or diabetes,” since whole grains can help regulate blood sugar. Not to mention, some gluten-containing foods offer things like B-vitamins, iron, and magnesium.

One study published in 2016 found that a “GF-diet was found to be poor in alimentary fiber due in particular to the necessary avoidance of several kinds of foods naturally rich in fiber (i.e. grain) and the low content of fiber of GF product that are usually made with starches and/or refined flours.”

Hopkins Medicine also reports that though “people who adopt a gluten-free diet often lose weight … it’s usually because they also cut out a lot of processed foods and refined carbohydrates that contain gluten.” As a result, weight-loss and feeling more energized is a result of “eating better, not [from] removing gluten.”

Dairy-free diet

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Background on this diet:

A dairy-free diet can be a standalone diet, or a natural consequence of other types of diets, such as a vegan diet or a strict Paleo diet.

What this diet entails:

A dairy-free diet means removing sources of dairy from your consumption, such as milk, cheese, butter, yogurt, and any other foods that have a milk-base, such as ice cream. Many people avoiding dairy products use a plant-based alternative, of which there are now many options, ranging from oat milk, to soy milk, to cashew milk, to coconut, and almond. There are also usually creamers, ice cream bases, and yogurts made from these plant sources that can act as alternatives to traditional milk-based dairy products.

Example dishes:

Breakfast:

Oatmeal (made with calcium fortified plant-based milk), with cinnamon, honey, almonds, and fruit
Roasted red pepper egg bites with whole grain toast
Breakfast burrito with poultry chorizo, avocado, fajita veggies, and salsa

Lunch:

Grilled salmon with grilled tomatoes and peppers and whole grain pasta
Tuna salad wrap with a side salad
Citrus shrimp quinoa salad

Snacks:

Calcium-fortified coconut yogurt with banana and hemp hearts
Almond butter on rice cakes
Popcorn with nutritional yeast

Dinner:

Roasted herb chicken with mushrooms, potatoes, and green beans
Gyro pita pockets with hummus and cucumber salad
Cuban bean stew with brown rice and a side salad

Potential health impacts:

A review published in 2016 assessed the evidence from a meta-analysis of observational studies and randomized controlled trials on “dairy intake and risk of obesity, type 2 diabetes, cardiovascular disease, cancer, and all-cause mortality.” The assessment found the following:

Intake of milk and dairy products seem to reduce the risk of childhood obesity
In adults, dairy intake “was shown to improve body composition and facilitate weight loss during energy restriction”
Milk and dairy was associated with either neutral or lowered risk of type 2 diabetes, as well as cardiovascular disease
Milk and dairy products were associated with a beneficial impact on bone mineral density, but had no association with risk of bone fracture
Dairy was “inversely associated” with colorectal, bladder, gastric, and breast cancer, while it seemed to be unassociated with pancreatic cancer, ovarian cancer, or lung cancer (its association with prostate cancer was inconsistent in the literature).
Dairy consumption was not associated with all-cause mortality.

It’s also worth noting that “having a proper peak bone mass and keeping it as long as possible is especially important for osteoporosis prevention” - this is likely because milk and dairy products are some of the “most important calcium sources” for many people. In that same vein, this same publication reminds us that elderly people should not avoid milk and dairy products if possible, since they are “a source of high-availability protein, vitamin D, calcium, and phosphorus, which are important for preventing disorders [such as] osteoporosis.”

Rejecting diet culture

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So here’s the thing: it’s an objective finding that most ‘diets’ don’t work. Before you think you wasted a bunch of time reading this article, hear us out: the way most diets are undertaken are unsustainable and unrealistic. This is because it’s not healthy or normal to live on under-consuming 500 to 1000 calories less than you need everyday; it’s not realistic to cut out your favorite foods forever after going cold-turkey; and it doesn’t make you a bad person or a ‘failure’ for gaining back the weight you lost on your diet within a year of quitting it.

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In fact, if you fall into the latter camp, you’re firmly in the majority. A study published in the British Medical Journal which analyzed 121 trials, enrolling “nearly 22,000 of overweight or obese adults who followed one of 14 popular diets, including Atkins, Weight Watchers, and the Mediterranean diet, for an average of six months … found that after a year or so the benefits are largely gone.” The exception to this finding, by the way, was the Mediterranean diet, which was the only diet to reduce LDL cholesterol 1 year out. So what’s the problem here?

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The problem is the way dieting is done.

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The reason weight is regained after finishing a diet (even with 5, or 10, or more pounds lost), is because the diet ends and you go back to your regular eating habits.

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The solution here? Forget picking up and dropping different diets for 6 months at a time each. Choose healthy lifestyle changes that work for you and stick with them long-term. This will be more likely to happen by default if you enjoy these changes. For instance, implementing more fruit and vegetables as part of a long-term change, adding exercise to your routine before work, or getting more sleep each night are all beneficial long-term changes, and if you can figure out how to implement them in an enjoyable way, you are more likely to consistently enact these positive changes day to day. As an example, if you want to get more sleep each night, consider going to bed an hour earlier, and an hour before that, turning off your phone and all sources of blue light: try reading or meditating before bed. See if you enjoy it. If not, that’s completely fine, but try to experiment with rewards and incentives for yourself to enact healthy, positive changes, and you will be more likely to stick with them.

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This also means making gradual changes that are designed to last a lifetime - as long as they work for you. As Harvard Health puts it, “it probably matters less what you pick [diet-wise] (whether low-carb, low-fat, or something in-between) than whether you stick with it.” So review the diets above, and see what might work best for you: it’s a common theme throughout most of them that increasing fruits and vegetables, and decreasing added sugars and processed foods, is a good thing for your health, so starting there may be a safe bet. Remember, though: change can be hard, and be kind to yourself throughout making these changes. Instead of reaching for perfection, just try for consistency.

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And remember - always consult with your doctor before making any dietary changes. You may also find it beneficial to consider working with a registered dietitian, as they can offer advice on what foods to increase and decrease to hit your goals, how to make sure you get all the nutrients and vitamins you need while making gradual dietary change, and even offer helpful meal plans and suggestions that make the process easier.

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