With the glutenous Thanksgiving break out of the way and New Year’s resolutions around the corner, many Americans will be considering starting a new diet.

But deciding which type is best for you can be a minefield, especially when sites like TikTok appear to be churning out a new fad diet every few months.

Intermittent fasting has emerged as the most popular calorie restriction form in the past decade. It’s almost impossible not to know someone who has shed at least some weight by eating within a strict time window or skipping meals entirely.

But while the weight-loss benefits are undeniable, the jury’s out on the long-term effects. A study last week suggested that regularly missing meals can raise a person’s risk of early death by 30 percent.

All-or-nothing types may veer towards extreme diets like the meat-only carnivore diet, which Joe Rogan and Jordan Peterson have credits for weight loss and better brain health – while also saying it gave them intense diarrhea.

Tradeoffs exist for all diets and vary from person to person. Use our guide to work out which of the seven most popular is right for you:

Mediterranean diet

Pros: Longer life, lower cancer risk

Cons: Calcium deficiency

Studies performed in the 1950s found that rates of heart disease were lower in countries like Italy, Greece and Spain than most countries in the west, which initially piqued the interest of scientists in the US.

Subsequent research confirmed that a diet rich in whole grains, vegetables, fruits, nuts, olive oil and fish carries various health benefits.

Others meats like chicken and beef are limited. The sugary highly-processed deserts are replaced with fruits and the occasional piece of dark chocolate.

Healthy fats, lower sugars and no processed foods keep a person’s arteries clear and healthy. 

Pop star Selena Gomez says that the Mediterranean diet even ‘saved her life’ after she was diagnosed with the autoimmune disease lupus in 2012.

Charlie’s Angels star Cameron Diaz, 50, credits the diet for her ‘graceful’ aging.

Doctors and nutritionists have sung the praises of it as well, with countless studies backing up claims that it can help fend off Alzheimer’s, cancer, heart disease and expand a person’s lifespan.

A Spanish research team described the diet as a ‘gold standard’ of preventative medicine in 2016 after a meta-analysis linked it to a higher quality of life and lower risk of chronic disease.

Researchers gathered data from 19 studies across 2015 and 2016 that found that people who eat these diets often have lower blood pressure, coronary artery disease, heart disease, and stroke rates.

In 2016, Italian researchers published a massive study that followed 1,712 people over 50 years to see how the diet would affect their lifespan. 

They found that those who followed a standard Mediterranean diet the closest lived an average of 4.4 years longer than their peers. 

Harvard University researchers were a part of a 2018 study finding that people who subscribed to the diet had biomarker indicators showing they were less likely to develop heart disease in the future.

Among the 26,000 participants, Mediterranean diet eaters had lower levels of inflammation, insulin resistance, hypertension and fats in the blood. 

They also had a lower BMI on average. 

A wealth of studies has tied the diet to lower cancer risks, and it can even be beneficial to a person after being diagnosed with the devastating disease.

World Health Organization researchers found in a 2010 study of 14,807 women that eating the diet could reduce breast cancer risk by up to 12 percent.

University of Texas researchers found last year men suffering from prostate cancer could stem the progression of the disease with a Mediterranean diet.

While the diet is packed full of many vitamins and minerals necessary for a person to live a long, healthy life, it does leave them short on calcium which is crucial to overall bone health.

Calcium is crucial to maintaining a strong skeleton, but the low amount of dairy products eaten daily can leave a person eating the southern European diet short of the mineral.

In a 2017 study, Spanish researchers found that only 25 percent of children aged six to excellent who ate the diet were reaching recommended levels of calcium intake for their age – potentially stunting their development.

An adult is recommended to consume 1,300mg of calcium every day. Calcium supplements can help fill this gap but are not considered to be as efficient as calcium derived from food.

This diet is also not for people whose plan is to solely lose weight, because the healthy and nutrient rich food can also be high in calories. 

Keto

Pros: Weight loss, low blood sugar

Cons: Kidney damage, calcium deficiency

Ketogenic diets, also called keto, are a rising trend, with stars like Kim Kardashian, LeBron James and Megan Fox reportedly using them in the past for its quick weight loss.

The diet involves dropping nearly all carbohydrates and instead replacing them with foods rich in fat and protein.

The aim is to go into ketosis, a theory that states a person starts to use fat as their primary energy source rather than carbs. 

The diet rose to prominence in the 1920s after early research found going keto could reduce the frequency of seizures in children who have epilepsy. 

In a report earlier this year, experts wrote that they had seen rapid weight loss among patients who took part in keto diets. They said drops in water and fat retention were the reason why.

They warn that the benefits are only short lasting, though. Over a year, the weight loss will slow and nearly match the standard diet and exercise.

A 2018 meta-analysis by researchers from Canada confirmed this, finding that people who used keto only lost one extra pound over 24 months when compared to people on a standard low-fat diet.

Burning so much weight, combined with a high protein diet that often avoids refined sugars can also reduce a person’s risk of developing diabetes. 

A Chinese meta-analysis 13 studies found people who ate the low-carb diet had their resting blood glucose level drop by 1.29millimoles per liter (mmol/L). 

The average non-diabetic has a resting blood glucose level of 3.9mmol/L to 5.6mmol/L. A level over 7mmol/L indicates that a person has diabetes.

Earlier this year, researchers at Stanford University found mice that used the high-fat diet had more resistant muscle cells – making them more likely and faster to recover from injury.

As a result, this made mice on a diet live longer than their peers who ate their usual diet during the study. There is no research proving a similar effect in humans, though.

Keto does come with downsides. People who subscribe to the diet often suffer severe deficiencies of vitamins and minerals that are found in carb-rich fruits and vegetables that they avoid.

In a 2017 report, Dr Hannah Holscher, of the University of Illinois, wrote the shortage in fiber could harm the body’s ability to absorb nutrients.

As a result, this can lead to inflammation and hurt immune function. 

When transitioning from burning carbs as a primary energy source to entering ketosis – where fat is burned – a person may also suffer from ‘keto flu’.

It is a temporary illness with symptoms such as headaches, fatigue, nausea, dizziness, and stomach aches.

The sickness is relatively mild, but the National Institutes of Health (NIH) warns that some will not be able to tolerate it.

The NIH says that a lack of calcium in the diet can also lead to low bone density.

Keto can also be incredibly harsh on the kidneys. A Chinese study from last year found that rats that took part in the diet for only four weeks experienced significant declines in kidney function.

It harmed processes that help regulate blood pressure and regenerate damaged cells to repair damage to the organ.

Low-carb diets have also been tied to increased heart disease mortality. 

A 2013 meta-analysis of 13 studies by Japanese researchers- including nearly 250,000 participants – found that people who ate the diets were 31 percent more likely to die of heart disease.

Intermittent fasting

Pros: Rapid weight loss, low cholesterol

Cons: Heart disease risk, low testosterone

Intermittent fasting is one of the most popular alternative diets, with tech moguls Jack Dorsey and Elon Musk singing its praises along with big-screen stars like Halle Berry and Hugh Jackman.

The diet sees a person limit their caloric intake to either certain hours or the day – or days of the week – to lose weight and control eating habits. 

Popular iterations include the 14:10 plan – where a person eats only within a 10 hour window each day and the 16:8.

Proponents of the diet say the highly regulated eating times prevent snacking throughout the day, which can quickly increase a person’s caloric intake without realizing it. 

Others use alternative day fasting strategies, like the 4/3 or 5/2 diets.

In both plans, a person eats normally for four to five days per week, then severely restrict their food intake to 500 to 600 calories on the other two or three days.

Studies have proved that intermittent fasting is effective at helping a person lose weight and treat obesity.

A Canadian meta-analysis of 27 trials published in 2020 found that people who used the diet plans could lose up to 13 percent of their body weight without serious adverse effects.

Weight loss can often come with unexpected benefits as well. 

Researchers at Salt Lake City, Utah’s, Intermountain Medical Center published a meta-analysis of five studies in 2015 that found extra benefits.

In the group of studies, people who used intermittent fasting were less likely to develop coronary artery disease or diabetes. 

For both, a drop in overall weight was cited as the reason for the decreased risk.

A Brazilian study published in 2018 found that people who took part in intermittent fasting recorded higher levels of HDL – dubbed ‘good cholesterol’ – and lower levels of the ‘bad’ cholesterol LDL and triglycerides.

High levels of LDL and triglycerides can lead to the walls of a person’s arteries hardening, restricting blood flow and increasing the risk of heart disease, a heart attack or stroke.

On the other hand, HDL removes harmful compounds from the body and reduces the risk of heart-related conditions as a result.

Experts warn that people who partake in this diet are vulnerable to binge eating and an unhealthy obsession with food.

A 2010 study by the Oregon Research Institute found that people who fasted were at an increased risk of binge eating or even suffering the eating disorder Bulimia. 

Until now, no long-term harms of intermittent fasting had been discovered. 

However, a study published in August by a University of Tennessee-led research team found that meal-skipping and abnormal food patterns can increase a person’s overall risk of death 30 percent.

The research, which included survey data from 24,000 people over 40, found that eating only one meal a day instead of three significantly increases mortality and heart disease risk.

Researchers could not determine whether the diet itself was at fault, or if other lifestyle factors were playing a role. 

University of Illinois, Chicago, researchers warned earlier this year that males who took part in intermittent fasting could also be at risk of having lower testosterone levels and a lower sex drive, even in young, healthy, men. 

The carnivore diet

Pros: Weight loss

Cons: Heart disease risk, diarrhea

As the name suggests, those who participate in the carnivore diet will mimic the eating patterns of the most ferocious beasts like the tyrannosaurus rex and the great white shark.

Carnivore diet eaters eat a diet almost entirely made up of meat and products that come from animals, like and eggs. 

It rose to popularity after Dr Shawn Baker, an author and orthopedic surgeon from New Mexico, published The Carnivore Diet in 2018. 

The book highlighted the alleged benefits of the zero-carb diet and became popular in some circles.

Dr Baker has emerged as a controversial figure in the medical community. His medical license was briefly suspended in 2017 for ‘incompetence’.

While nutritionists and dieticians have rarely backed the diet, Canadian psychologist and media personality Jordan Peterson and his daughter Mikhaila have praised its anti-inflammatory properties. 

Popular podcaster Joe Rogan has said that he temporarily tried the carnivore diet as well. 

Like keto, it is highly effective at burning weight and fat, as it cuts out carbs as the body’s primary energy source and uses fat instead.

Meat is a low calorie source of energy as well, assisting in weight loss even more. 

Little research has been done on the carnivore diet, which is still a fringe diet with relatively new origins.

Some experts warn that eschewing fruits and vegetables can lead to severe vitamin C, E and fiber deficiencies.

A diet made up entirely of meat and eggs can lead to high blood pressure, and heart problems.

Mr Rogan said that that he suffered extreme diarrhea when trying the diet – a known side-effect of all meat and high meal diets.

The paleo diet

Pros: Better metabolic health, low cholesterol

Cons: Heart disease risk, low testosterone 

Despite millions of years of nutrition and food science advancements, some people still choose to eat like cavemen- and their health may benefit from it.

The paleo diet is a style of eating that ditches foods that were not available to our earliest ancestors. This mainly includes meat, fruits and vegetables.

The idea is that the body has not evolved to eat modern food – and instead is better eating the same way our distant ancestors did.

Foods that came from human ingenuity, like milk and dairy products, grains, beans, gluten and refined sugar, are pushed to the side.

Highly processed foods that are all too common in the modern diet are also ditched.

Hollywood stars Anne Hathaway, Blake Lively and Miley Cyrus are among those that report using the diet.

The diet is similar to keto, as many carb-rich foods like bread and rice are abandoned. 

Vegetables like broccoli, carrots and potatoes – that a ketogenic person may avoid – can give a person on the paleo diet their fix of carbs, though.

A 2015 meta-analysis of four studies, with a combined 159 participants, found that people who switched to a paleo diet during a study period saw their waste measurements drop more than those on other diets.

They also showed signs of a stronger metabolism, including lower blood pressure, and lower levels of LDL or triglycerides.

Paleo participants also recorded higher levels of HDL, the good cholesterol. Diabetes risk for this group was lowered, and their resting blood glucose level fell.

It can also be a tool for people with diabetes to manage their condition better.

Researchers from the University of California, San Francisco, found in 2015 that type 2 diabetics who switched to a paleo diet had greater control of their blood sugar and blood that was more sensitive to insulin.

They also showed similar biomarkers indicating their metabolic health had improved since they started the diet.

In the most extreme examples, people will adopt forms of the carnivore diet where the even eat raw meat – swearing off cooking as a modern form of food preparation.

Cutting out all processed foods from a person’s diet can be extremely beneficial to a person’s health, however.

Earlier this month, experts told DailyMail.com that the foods were as harmful as cigarettes to the average person – and were linked to cancer, Alzheimer’s, diabetes and more.

These modern processed foods are often packed with harmful chemicals, sugar and calories with little nutritional value.

This type of diet can lead to some vitamin deficiencies. Studies find that cutting out dairy products can lead to a severe drop in calcium intake.

A Swedish research team published a 2007 study finding that despite overall improvements in health, people who switched to a paleo diet were only getting half as much calcium from their diets.

Harvard University experts also warn that the paleo diet could leave a person deficient in B vitamins.

This results from dropping dairy products and beans, both of which are excellent sources of the vitamin group.

Vitamin B deficiencies are linked to nerve and brain damage, and could put a person at risk of suffering a stoke. 

Vegetarian and pescatarian

Pros: Healthier weight, lower heart disease and cancer risk

Cons: Anemia, increased stroke risk

The most popular alternative diet in the world is vegetarian. 

Emerging thousands of years ago, many have sworn off animal meat for spiritual reasons, health, or love for the creatures.

Some who want to avoid meat but still indulge in seafood may opt for a pescatarian diet, where a person eats fish but avoid poultry, beef, pork and other meats.

Around one-in-five people on earth are vegetarian, including The Queen’s Gambit star Anya Taylor-Joy, and are likely enjoying many health benefits.

Research led by Saint John’s University and published in 2008 of 2,500 young Americans between 15 and 23 found that vegetarians were less likely to be obese.

Scientists chalked this up primarily to vegetarians having a diet that included more fruits and vegetables – which generally have fewer calories and can be more filling than meat products.

They worryingly did find higher rates of binge eating and other unhealthy food behaviors among the vegetarians in the group.

Vegetarians will often have better control of their cholesterol as well. 

A 2017 meta-analysis led by Japanese researchers found across 49 studies and 8,385 participants that vegetarians had lower levels of cholesterol and triglycerides on average.

In turn, they are also less likely to suffer from heart disease, according to a University of Oxford study published in 2019 that took place over 18 years and included nearly 50,000 participants.

Researchers found that vegetarians and pescatarians had 13 percent lower rates of heart disease than people who ate meat.

In the Oxford study, the non-meat eating group was at a 20 percent increased risk of suffering a stroke.

Previous research has tied the lack of B12 in vegetarian diets to the increased risk of stroke.

Earlier this year, another University of Oxford study that followed 54,000 participants over 11 years found decreased risk of multiple types of cancer.

Vegetarians are two percent less likely to suffer any form of cancer, nine percent less likely to develop colorectal cancer and postmenopausal women were at an 18 percent reduced risk of breast cancer. 

Removing meat from a person’s diet can lead to iron deficiencies. 

Not getting enough of the mineral is linked to anemia, a condition where a person is not producing enough red blood cells.

Men and women over 50 should get at least 8.7mg of iron daily. Women under 50 need 14.8mg daily.

Anemia can severely restrict oxygen flow to the brain and other crucial organs in the body.

A third University of Oxford study, published in 2019, found that 3.9 percent of vegetarians suffered from the condition.

Only 2.9 percent of meat eaters have anemia – a rate 35 percent lower than vegetarians. The study also found 6.6 percent of vegans had the condition.

This can be especially harmful for older people, where calcium deficiencies lead to brittle bones and the development of bone-stripping arthritis. 

Vegan

Pros: Low heart disease and cancer risk

Cons: Anemia, calcium deficiency 

A vegan diet is a more intense and restrictive version of the vegetarian diet where a person cuts out meat and all animal products.

The diet has become increasingly popular in recent years, with famous figures like popstar Billie Eilish and Formula 1 driver Lewis Hamilton both sharing they were vegan in recent years.

It is very similar to the vegetarian diet, though a vegan will also cut out milk and dairy products. 

Some vegans even oppose using animal products in general – swearing off leather, fur clothes or other non-food products with material harvested from animals. 

Because dropping meat is a primary dietary change for both vegans and vegetarians, the decreased risks of heart disease, cancer and obesity that apply to the latter are enjoyed by the former as well.

The lack of meat consumption also puts them at an increased stroke from vitamin B12 deficiency and anemia from not getting enough iron.

The big difference between the diets is the abandonment of dairy products. 

Like other styles of eating that do not include dairy, this puts vegans at risk of calcium deficiency. 

These calcium deficiencies leave vegans with potentially weaker bones, increasing their risk of skeletal injuries.

A 2008 Oxford study of over 30,000 people found that vegans were 30 per cent more likely to suffer a fracture anywhere on their body.

Researchers in Spain performed a meta-analysis of 20 studies – combining data from 37,000 participants – finding that vegans and vegetarians had lower bone mineral density.