Diet Types

Diet types cater to diverse health and ethical preferences. Low carbohydrate/high protein diets like Keto focus on fats for weight loss, while low fat/high carbohydrate diets emphasize heart health. Plant-based, vegetarian, and vegan diets exclude animal products, chosen for health or ethical reasons.

Different Diet Types & Benefits

Healthy nutrition plays an essential role in reducing cardiovascular risk and heart disease. In 2015, an estimated 630,000 Americans died from heart disease, of which 366,000 died due to coronary artery disease. [1] The mortality rate secondary to heart disease rose in 2015 by 1%, although it gradually declined over four decades, most likely due to the obesity epidemic. [1]

Conventional diets generally include a macronutrient composition of 30% fat, 50% carbohydrate, and 20% protein. Although all individuals should be encouraged to follow a heart-healthy lifestyle, the limitation of scientific evidence with a variety of available diet formats leads the public more confused about choosing the best diet type. Here, we will discuss various diet types available and their effect on heart disease with published scientific evidence.  

Low Carbohydrate & High protein Diet 

What are Low carbohydrate and high protein diets (LC/HP)? 

LC/HP diet contains a large amount of protein and a significantly lower amount of carbohydrates. Although there is various carbohydrate restriction with a broad spectrum of LH/HP style, one can start from limiting carbohydrate intake less than 100 g/day with protein consumption at least more than 0.8 g/kg of body weight or >20% of daily calories count. [2] 

Based on 2000 Kcal diet

  • Atkins diet: 2 types – LC (~20-30 g/day), High protein and high fat diet – 2.3 g protein/kg/day (35%), 6% carb, 59% fat. [3] 
  • Zone diet (LC/HP): Protein >2-2.3 g/kg/day (34%), 36% Carbohydrate, 29% fat [4] 
  • South Beach diet (LC/HP): Protein ~2.6 g/kg/day (39%), 28% Carbohydrate,33% fat [4] 
  • Stillman diet (Very low carb): Protein ~ 4.3g/kg/day (64%), 3% Carbohydrate,33% fat [4] 
  • High protein normal carbohydrate: Protein ~1.3-1.4 g/kg/day (21%), 50% Carbohydrate,29% fat [5] 
  • USDA 2015-2020 guideline: Protein 10-35% of total calories, 45-65% Carbohydrate, 25-35% total fat with <10% of saturated fat [6]

Weight Loss

Low-carbohydrate with the combination of high-protein diets (LC/HP) have gained widespread popularity to control weight. The concept is mainly driven due to the potential deleterious effect of carbohydrate consumption, while LC/HP could lead to better weight management or even weight loss.[7] Foster et al. performed a one-year duration randomized controlled trial involving 63 obese men and women who were assigned to either a low-carbohydrate, high-protein, high-fat diet or a low-calorie, high-carbohydrate, low-fat (conventional) diet. The finding showed a short-term weight loss (4% more) with a low carbohydrate diet. [8] However, the difference disappeared in one year.  

Trichopoulou A and colleagues performed a study to demonstrate the impact of LC/HP diet on mortality rate. Participants were 22 944 healthy adults whose diet was assessed through a validated questionnaire over 10 years period. The findings showed that prolonged consumption of diets with LC/HP is associated with a ~22% increase in total mortality. [9] Moreover, another study from ARIC showed an 18% increase in mortality rate with low carbohydrate diets using animal-derived protein and fat sources (e.g., lamb, beef, pork, chicken), but plant sources (e.g., vegetables, nuts, peanut butter, whole-grain bread) were associated with lower mortality rate. [10] 

The concern regarding renal function is – how much protein can we consume without impacting renal function?  

A study including 1,624 individuals on a high protein diet (~76.6 g/day – 50% of recommended protein intake) analyzed blood samples for serum creatinine and glomerular filtration rate (GFR). The conclusion was high protein intake not associated with renal dysfunction in women with normal GFR while it may probably increase GFR in those with mild renal insufficiency [defined as a serum creatinine of 0.88 mg/dl (range 0.77 to 1.09 mg/dl) and a GFR of 71.0 ml/min/1.73 m2.2]. [11] 

Rather than emphasizing specific food categories, we should focus on a healthy diet such as lean protein, vegetables, fruits, and whole grains. Carbohydrates can be divided into two groups, simple or complex forms based on underlying chemical structure. Simple carbohydrates are digested quickly with a rapid increase in blood sugar level, whereas digestion of complex carbohydrates is slower with a gradual release of glucose into the bloodstream. Therefore, the recommendation from AHA is to limit processed, refined simple sugar while getting more complex carbohydrates.  

Among various protein sources, we should choose more healthful protein sources instead of red meat. Good protein options are Fish, chicken, turkey, lean meats, low-fat dairy products, whole grains, nuts, beans, and legumes.  


Low Fat & High Carbohydrate Diet 

A low fat/high carbohydrate diet (LF/HC) is considered an alternative option to lower total fat intake, including saturated and trans-fat, while increasing carbohydrate intake. Although low carbohydrate consumption may allow your body to burn fat, it can paradoxically promote unhealthy fat absorption. An alternative hypothesis is that eating an LF/HC diet may stimulate a better physiological response for burning fat and weight loss.  

In the REGARDS study, it had shown that trans-fat was associated with a higher all-cause mortality rate. [1] A study done by the National Institutes of Health showed that LF/HC diet was associated with increased fat loss compared to a low carbohydrate/high-fat diet.[2] Women’s Health Initiative study reported that those on a low-fat, high-carb diet lost more weight over a seven-year interval among women. [3] 

However, the effect of low or high carbohydrates on cardiovascular health remains controversial. In 2017, Prospective Urban Rural Epidemiology (PURE) study was performed, including 135,335 individuals from 18 countries across five continents with a median follow-up of 7·4 years. The study reported that high carbohydrate intake was associated with increased risk of mortality while saturated and unsaturated fats were not significantly associated with risk of myocardial infarction or cardiovascular disease mortality. [4] 

However, the limitations of those studies are as follows. The quantification of carbohydrate intake was mainly specific to the population studies due to internal reference and failed to account for the potential effects of food sources (i.e., animal-based versus plant-based). Therefore, Seidelmann SB and colleagues attempted to investigate the association between carbohydrate intake and mortality. Both high (>70%) and low percentages (<40%) of carbohydrate intake were associated with increased mortality, with minimal risk observed at medium carbohydrate intake (50–55%).[5] 

We should focus on healthy food from each category (fat or carbohydrate) rather than the general classification. Concerning carbohydrates, we must avoid simple carbohydrates and high processed ones as it could cause dramatic alteration in blood glucose levels. Low fat intake is vital to control daily calorie intake as well as blood cholesterol. One should aim to avoid saturated fat and trans-fat (such as fatty beef, lamb, pork, poultry with skin, beef fat (tallow), lard, butter, and cheese) and encourage to eat more poultry, fish, nuts, and whole grain.  

Carbs to Avoid Carbs to Eat
White bread  Whole fruits, Nuts
Potatoes  Whole grain
Cornflakes  Non-starchy vegetables
Rice crackers  Legumes
Fruit juice 
White rice 

Whole grains: quinoa, amaranth, buckwheat, steel-cut oats, muesli, barley or wheat bran

Non-starchy vegetables: artichoke, broccoli, leafy green vegetables, eggplant, Brussels sprouts, tomatoes, cucumber

Legumes: chickpeas, black beans, kidney beans 


Plant-based diets vs. Lacto Ovo Vegetarian vs. Vegan Diet  

What are different types of vegetarian diets? 

Plant-based diets mean that the diet is mainly comprised of plant food. However, the option to eat certain animal-derived products allows. 

LactoOvo vegetarian diet is a plant-based primarily diet including dairy and eggs and without meat, fish, and poultry. It is like a plant-based diet and has many health benefits 

A vegan diet is another type of vegetarian with complete exclusion of all animal products. Vegetarians don’t eat meat but can consume animal-derived products like cheese and honey.

Pescatarians eat fish and shellfish without red or white meat. 

Flexitarians, semi-vegetarian, eat mostly plant-based food while consuming meat occasionally. 

Potential benefits of Vegan Diets

Moreover, plant-based diet or vegetarian diet had shown to be associated with cardiovascular benefits and the correction of CKD-accompanying complications, partly due to the inclusion of large amounts of dietary fibers, n-6 fatty acids, folic acid, potassium, magnesium, vitamin E, vitamin C, and carotenoids, as well as many phytochemicals. [8] The finding was verified in other studies, which demonstrated a lower risk of coronary artery disease while improving risk factors such as better blood pressure control, decreased atherosclerosis. [9,10] 

Plant-based diets have been associated with a lower risk of coronary heart disease based on small and observation studies. [1,2] However, the type of plant-based diets were poorly characterized in these studies as simple carbohydrates from refined grains and sugar-sweetened beverages are associated with higher cardiovascular risk. [3,4] 

Satija A and colleagues performed a population cohort study to analyze the cardiovascular risk of healthful and unhealthful plant-based diets. The plant-based diet was divided into three categories- healthy plant-based diet index (hPDI), which includes healthy plant foods (whole grains, fruits/vegetables, nuts/legumes, oils, tea/coffee), less-healthy plant foods (juices/sweetened beverages, refined grains, potatoes/fries, sweets), and unhealthful PDI. The study showed that a higher intake of a plant-based diet index rich in healthier plant foods is associated with substantially lower CHD risk. In contrast, a plant-based diet with less-healthy plant foods is associated with higher CHD risk.[5] A post hoc analysis from the PREDIMED cohort that assessed participants based on pro-vegetarian food patterns showed that high adherence to a diet composed primarily of plants and lower in animal-derived foods resulted in a 41% relative risk reduction compared to the lowest adherent group.  

As not all plant-based diets are created equal, clinicians should remind their patients of less healthy plant food while sugar-sweetened and sweetened beverages are linked to increased risk for diabetes, and sweets and refined carbohydrates are associated with increased risk for coronary events. [6,7] 

It can help to prevent or lower the risk of developing type 2 diabetes. [11,12] 

Due to higher fiber content, digestion is slower and improves blood sugar control.[13] 

Moreover, vegetarian diets help maintain a healthy weight as it has higher fiber content, resulting in fullness and reduce overeating.  

In a large study (37,875 participants) of finding correlation of BMI with different diet patterns, vegetarians and fish-eaters had lower BMI than meat-eaters. [14]

What to do in daily life? 

Plant-based or Vegetarian diets are a healthy diet and a way to avoid unhealthy fat, animal products, refined grains, and sugars while eating plenty of healthy plant foods. Overall, a plant-based diet is an excellent choice to take care of your health and the planet.  


Mediterranean Diet 

The Mediterranean diet is a particular type of traditional diet from the countries near the Mediterranean Sea, such as Greece, Italy, France, and Spain. There is no standardized format for Mediterranean diets; instead, each country has its own culture and styles. Moreover, the Mediterranean diet type emphasizes the specific kind of diets rather than calories or macronutrients.  

A Mediterranean diet style mainly includes the following: 

  • fruits, a wide variety of vegetables, bread, nuts, seeds, legumes, beans, and whole grains 
  • Healthy fats, olive oil
  • Poultry, Dairy, Fish, seafood, eggs, and red wine in moderate amount 

Foods to avoid: 

  • Processed foods and meats: Chips, fast food, popcorn, sausage, bacon 
  • Sugars and sweetened beverages: Soda, Juice, Sport and energy drinks 
  • Refined grains or carbohydrates: White rice, white bread, pasta, flour tortillas 
  • Saturated fats  

Processed meats are any meat preserved by smoking, curing, or salting, or additional chemical preservatives. 

Potential benefits of a Mediterranean diet 

The Mediterranean diet has been studied in scientific literature and showed one of the healthiest diets available for several health problems.  

PREDIMED study had done a multicenter trial including 7444 participants assigned to three diets style- Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a control diet (advice to reduce dietary fat). The Median follow-up was 4.8 years. It showed a 30% decrease in vascular events. The Mediterranean-style diet is higher in extra-virgin olive oil or mixed nuts than the reduced-fat diet category. [1] 

The Lyon Diet Heart Study was a secondary prevention trial that reported a 72% reduction in cardiovascular events in the alpha-linolenic acid-rich Mediterranean-style diet group compared with the control group following a prudent Western-style diet. 

The Mediterranean diet invigorates eating nutrient-rich foods and limits processed food and sugars. So, it can promote weight loss if one can pair it with a healthy lifestyle.  

One of the largest cohorts, including 32,119 members, attempted to investigate the impact of a Mediterranean diet and long-term changes in weight and waist circumferences. The conclusion was that long-term adherence to the Mediterranean diet is associated with reduced weight gain and reduced waist circumference increase over five years. [3]

Several observational and randomized studies have shown the weight loss effect of a Mediterranean diet. Therefore, a meta-analysis of five RCT, including 998 individuals – comparing the Mediterranean diet to a low-fat diet, low carbohydrate diet, and American Diabetes Association diet. The finding was that the Mediterranean diet produced similar weight loss as other diets style (i.e., low fat or low carbohydrate) at 1-year duration with an average weight loss of 10-22 lb. [4]

Recently, clinicians or dietitians started to think of using the Mediterranean diet in peri/postmenopausal women to intervene in menopause-related obesity. While retrospective analysis showed some promising effects, a future randomized study is required to verify the hypothesis. The research was done by Ford C and colleague to evaluate diet pattern and weight gain in postmenopausal women (Women’s Health Initiative Observational Study). The finding was interesting and suggested that a low-fat diet may promote weight gain, whereas a reduced-carbohydrate or Mediterranean diet may decrease the risk of postmenopausal weight gain. [5]

MedDiet is found to have a protective effect against diabetes mellitus.  

One large randomized study, PREDIMED-Reus nutrition intervention randomized trial, attempted to find the impact of MedDiet on the incidence of diabetes. Participants were randomly assigned to education on a low-fat diet (control group) or to one of two MedDiets, supplemented with either free virgin olive oil (1 liter/week) or nuts (30 g/day). When the two MedDiet groups were pooled and compared with the control group, diabetes incidence was significantly reduced by ~52%. [6] 

Moreover, those with DM may have better glucose control and lower HbA1c if they follow greater adherence to a Mediterranean-type diet. A study from South Italy conducted a cross-sectional analysis in 901 outpatients with Type 2 diabetes. The lower level of blood glucose and  HbA1C was found in those with long-term adherence to a Mediterranean-type diet.[7]

Coronary atherosclerosis represents the most common pathological substrate of coronary artery disease, and the characterization of the disease as a chronic low-grade inflammatory condition is now largely accepted. Moreover, chronic inflammation could contribute to the development of cancer, diabetes, and dementia.  

Researchers sought to assess the effect of MedDeit on the inflammatory maker and 598 individuals involved in the study. Various inflammatory markers such as adiponectin (AD), leptin, tumor necrosis factor-alpha (TNF-α), plasminogen activator inhibitor 1 (PAI-1), and high-sensitivity C-reactive protein (hs-CPR) were measured. The present study showed that adult males with higher adherence to the MD showed a better inflammatory profile than the group with lower adherence.[8] Another report from Casas R group showed long-term adherence to MeDiet could decrease the plasma concentrations of inflammatory biomarkers related to different steps of atheroma plaque development in elderly persons at high cardiovascular risk.[9] 

How do you apply this diet to daily life 

No doubt the Mediterranean diet is a healthy eating pattern. It encourages eating nutritious foods like vegetables, fruits, whole grains, beans, legumes, low-fat or fat-free dairy products, fish, poultry, non-tropical vegetable oils, and nuts while limiting processed food and sugars.  

A Mediterranean diet will help enhance a healthy heart and reduce various cardiovascular risk factors – blood pressure control, sugar control, and reduce inflammation.  


Ketogenic Diet 

The diet consists of high-fat content and very low carbohydrate, which is somewhat similar to a low carbohydrate and high-fat diet. The idea behind including a higher range of a fat diet is to steer the body’s energy metabolism into burning fat rather than carbohydrate. 

What is Ketosis, and where does it come from? 

Ketone bodies are the water-soluble molecules containing the ketone group produced by the liver from fatty acids during periods of low food intake (fasting), restrictive carbohydrate diets, starvation, prolonged intense exercise, alcoholism, or untreated (or inadequately treated) type 1 diabetes mellitus. 

Ketosis is a metabolic condition of your body, which burns fat for an energy source instead of carbohydrates. The entrance to ketosis limits carbohydrate intake while increased consumption of natural fats and protein—such as meat, fish, and poultry. 

Potential benefits of a Ketogenic diet

One of the questions is Is Keto Diet Safe? especially with cholesterol levels. Generally, a low carbohydrate, high protein, and fat diet are potentially unhealthy as it may cause a rise in LDL cholesterol and TGs, and this issue is of particular importance in obese individuals. Multiple studies demonstrated that reducing carbohydrate intakes could lower total cholesterol and blood triglycerides level while increasing HDL cholesterol levels. [1,5] Furthermore, Keto Diets have been reported to increase the size and volume of LDL-C particles along with the reduction of cardiovascular disease risk. [6] 

There is ample supportive evidence of using Keto diets for weight loss therapy, but the underlying mechanisms remain unclear. [1] Although it is difficult to pinpoint an exact mechanism, we have probable hypothesized mechanisms of Keto Diet’s weight loss effects: 

  1. Reduction in appetite due to higher protein intake and possible direct appetite suppressant action of the ketone bodies. [2]
  2. Increase fat utilization. [3]

Moreover, a very low carb, a ketogenic diet was more effective for long-term weight loss than a low-fat diet, resulting in extra weight loss with an average of 2 pounds (0.9 kg). [1] Another research in 34 elder adults was done comparing keto diet and low-fat diets. In 8 weeks, the keto group had 3-fold greater decreases in belly fat than the LFD group and 5-fold greater reductions in total body fat mass in the keto group. [4] 

Overall, the Keto diet could lead to a more significant reduction in body weight than a low-fat diet while providing a feeling of being sated.  

Some people believe that it’s dangerous when your body enters ketosis. However, it’s essential to understand the difference between ketosis, which is nutritionally safe, and ketoacidosis, which is caused by a lack of insulin and can increase blood sugar significantly. 

The use of keto diets in DM has been tested in many research studies. One study showed improvement in insulin sensitivity up to 75% while reducing HbA1C. [7] A recent study of the Keto diet in the diabetes population demonstrated a significant reduction in hemoglobin A1C, body weight, blood pressure, and cholesterol level. [8] Another study tested the effect of the Keto diet on 84 individuals with diabetes and reported a significant reduction in blood sugar levels. Moreover, Five individuals who were taking over 20 units of insulin at baseline were no longer taking insulin at the end of the study. [9] 

The Keto diet may reduce or improve other health-related problems such as cancer, dementia, Parkinson’s disease, and epilepsy in children. [10-13] 

Keto Diet in daily life

The most important thing to do is to avoid eating too many carbs. It would be better to keep carbohydrate intake under 50 grams per day, ideally below 20 grams. You should plan your meal based on the following:  

  • fatty Fish: salmon, tuna, and mackerel 
  • eggs 
  • butter and cream: grass-fed butter and heavy cream 
  • cheese: like cheddar, cream, or mozzarella 
  • nuts and seeds: almonds, walnuts, flaxseeds, pumpkin seeds, etc. 
  • healthy oils: extra virgin olive oil and avocado oil 
  • avocados: whole avocados or freshly made guacamole 
  • low carb veggies: green veggies, tomatoes, onions, peppers, etc. 
  • meat: red meat, steak, ham, sausage, bacon, chicken, and turkey   


Intermittent Fasting 

Intermittent fasting is one of the popular diet patterns in fitness and is used for various purposes such as weight loss, improving overall health, and lifestyles. It is not a particular type of diet; instead, an eating pattern emphasizes a specific eating and fasting period.

Intermittent fasting has been practiced in various structures throughout human history and religious reasons, including Buddhism, Judaism, Christianity, and Islam. 

The basic concept of intermittent fasting is to reduce overall calorie intake, hence enhance weight loss if you don’t make up by eating more foods during eating periods. 

The story of Intermittent fasting:  

Although intermittent fasting has been around for ages, it got the media and people’s attention after the BBC broadcast “Eat Fast, Live Longer” and “the Fast Diet” by Dr. Michael Mosley. It further emphasized “The Obesity Code” by Dr. Jason Fung in 2016.   

What is the scientific explanation of the benefits of fasting?

When you are not eating or fasting, several hormonal changes happen in your body. Whenever we eat, the food is broken down into glucose or sugar and enters the cells with the help of insulin. If you have extra calories and our cells don’t use glucose, excess glucose will be stored as fat cells.  

During fasting, insulin levels go down, and fat cells start to be used as an energy source. Hence, the whole processes improve insulin sensitivity and promote weight loss. [1] 

Evidence from animal and human studies suggested improved cellular repair, increased level of growth hormone, and many health conditions such as cardiovascular disease, diabetes mellitus, cancers, neurologic disorders, and antiaging. [2] 

Different Methods of Intermittent Fasting 

It is known as Leangain protocol. The schedule involves 16 hours fasting and 8 hours eating period.  

It involves limiting your calorie intakes up to 500-600 calories for two days and normal intakes for five days.  

It includes eating a normal diet one day and fasting or eating a reduced calorie intake the other day. 

The schedule includes 24 hours fasting one-two day a week.  

It involves small meals, including fruits and vegetables during the day, and one large meal at night.  

This meal’s style is that you don’t need to follow a structured fasting plan; instead, you skip one to two meals when you don’t feel hungry or have time to eat.  

Which method is better than others? 

There is no evidence of superiority among different methods. Therefore, you should use whatever way is convenient for you.  

However, if you decide to try intermittent fasting, be mindful of food quality. Ensure you eat healthy food and avoid junk food during the eating period as much as possible. 

What are the side effects? 

The most common one is hunger. Moreover, you may also feel tired, not able to think, and weak. It may take some time for your body to adjust to the new meal schedule.  

Suppose you have underlying medical conditions such as diabetes, eating disorders, pregnancy, gastroesophageal reflux, and women with menstrual disorders. In that case, you should talk to your physician before you start doing intermittent fasting. 


Western Diet

The diet is characterized by high intakes of processed meat, red meat, fried foods, high-fat dairy products, eggs, pre-packaged foods, butter, added sugar products, and low intakes of Fish, fruits, vegetables, whole grains, nuts, and seeds.

Western Diet and Potential Health Implication 

Earlier studies reported support the association between a western diet and increased risk of coronary artery disease, diabetes, cholesterol problem and cancer. [1,2] Moreover, prolonged consumption of western style calories rich diet could even evoke a state of chronic metabolic inflammation, which could contribute to multiple health problems including obesity-associated metabolic syndrome, type 2 diabetes mellitus, non-alcoholic fatty liver disease, cardiovascular diseases, Alzheimer’s disease as well as certain cancers (i.e., colon cancer, pancreatic cancer, and breast cancer). [3] 

Therefore, researchers are trying to define certain dietary intake patterns with metabolic activity resulting in oxidative stress, insulin resistance, and lipid dysregulation. In the latest study done by Chandler PD and colleagues, they attempted to map out metabolic signatures between two dietary patterns; western vs prudent dietary pattern. Prudent dietary pattern is mostly consisted of fresh fruit, vegetables, grilled Fish and salad. 2199 Women’s Health Initiative (WHI) participants were included. The finding was positive association of oxidative stress and abnormal lipid metabolism, resulting chronic inflammation, with western diet whereas prudent dietary pattern was not. [4] 


What is the best diet type in daily life? 

Although there are multiple research trials regarding correlation with dietary patterns and cardiovascular events, hard endpoints-based trials are, however, still limited. Nevertheless, choosing a healthy diet is not very hard as you think. Mediterranean and plant-based diets are known to be good healthy foods available. As there are multiple food options available, it is paramount to emphasize the type of food you eat, rather than following a specific type of diet.  

The healthy diet mostly should include the following:  

    • Plenty of vegetable fruits and whole grains (i.e. whole oats, whole wheat, whole-grain rye, buckwheat, Bulgur Wheat, Millet, Whole Barley, Quinoa, Brown Rice, Corn, Pop Corn) 
    • Low-fat and non-fat dairy
    • Skinless poultry, Fish
    • Beans and legumes
    • Vegetable oils
    • Nuts and seeds

    We should limit fat, trans fat, sodium (less than 23,00mg per day), sugar-sweetened beverages, processed meats, and alcohol in moderation. Remember how many calories you should eat everyday although it depends on multiple factors including age, gender, and daily physical activity.