How do you make food decisions? Is cost or environment your biggest concern? Or are you following one of many diets you might discover online or elsewhere, like the carnivore diet, or veganism or the Mediterranean diet.

Diet choices are hard. You might feel intimidated by fears over the time, effort and the knowledge required to cook your own meals, or you might be confused over what various social media influencers are telling you online, or by the ads you see on television.

Log in to TikTok and you might be confronted by the Liver King, who wants you to know he eats a cup of raw liver as part of each one of his meat feasts, or the discredited celebrity chef Pete Evans extolling the virtues of bone broth.

You can’t watch your favourite show on commercial television without seeing a promotion for some kind of foodstuff. One study from 2016 found that 11% of television ads were for food, with the most frequently advertised being snack foods, fast foods/take away meals and sweetened beverages.

Let’s be clear, when seeking diet advice, you should seek out an Advanced Accredited Practising Dietitian and Nutritionist, of which I am one, as that accreditation shows they have done the work to become a qualified, evidence-based dietitian with both a university degree and verification from an independent professional body.

In this article I compare five diets—vegan, vegetarian, keto, carnivore and Mediterranean— comparing on the impacts on your health and busting some myths along the way, to help you make an informed choice about what you decide you need to consume.


A vegetarian diet avoids flesh foods, such as meat, fish, and poultry, and relies on plant foods like fruit, nuts, cereals, legumes, and vegetables to meet nutritional requirements. Some people who choose a vegetarian diet still eat eggs and fish.

The high vegetable intake that’s a feature of this diet means it has good fibre intake and a great range of vitamins and minerals. Considering 90% of Australians do not eat the recommended five servings of vegetables and two servings of fruit daily, a vegetarian diet can help you get closer to these requirements.

People who follow this approach do not eat meat or other animal proteins. As such, they tend to have lower saturated fat intake, better cholesterol/triglycerides levels, and a reduced risk of cardiovascular disease.  People often lose weight by going on a vegetarian diet.

The biggest disadvantage of a vegetarian diet is that it is hard to get adequate protein, iron, vitamin B12, and calcium. People who choose this approach must eat other non-animal foods (e.g., nuts, lentils, pulses, tofu etc.) to get adequate intake of these essential nutrients. 


This diet is a strict vegetarian diet that does not include ANY animal-sourced products. This consists of no flesh foods, dairy products, eggs, or food sourced from an animal (e.g., honey) in their diet.

The advantages and disadvantages of this diet are similar to that of a vegetarian. In addition, though, Vitamin b12 is mainly sourced from animal products, so it is very difficult to get adequate b12 intake. For people less than 18 years old whose muscles and bones are still developing, I would not recommend this diet as it is difficult to meet nutritional requirements.

Practical tip: For vegetarian and vegan diets, I recommend people get regular blood tests (every six months) to assess their levels of all vitamins and minerals and supplement if they are low. I would also recommend that you seek professional advice (from a dietitian or a doctor) to ensure you meet nutritional requirements.


Named initially because it was identified as being from the Mediterranean region, this diet contains a wide variety of nutritious foods. It typically includes fruits, vegetables, whole grains, legumes, nuts, seeds, dairy products (milk, yoghurt, cheese), lean meats (fish, chicken, lean red meat) and heart-healthy fats (olive oil, avocado).

Processed foods, including added sugar and refined grains, should be restricted. Plenty of water, a moderate amount of alcohol and social interaction through food are also vital parts of the Mediterranean diet.

This diet provides the widest variety of all vitamins and minerals and has foods from all core food groups. A Mediterranean diet can promote weight loss and help prevent heart attacks, strokes, type 2 diabetes, and premature death. A Mediterranean diet may be tied to a lower risk of dementia, cognitive impairment, and Alzheimer’s disease.

What are the disadvantages of the Mediterranean diet? There are none! It’s a very good diet. In fact, it’s what the Australian Dietary Guidelines are based on.

Practical tip: Our dietary guidelines are based on this approach, and it is the one that most dietitians will use to guide their approach.

Ketogenic or Keto

This is a restrictive diet. Although it has various forms, the common feature of keto diets is that they restrict carbohydrates and focus on foods that are mostly fat or protein based. In a ketogenic diet, you avoid some core food groups (grains and cereals) and, in some cases, dairy products.

Weight loss is one of the main advantages of keto diets and it’s a major reason why people choose it. Reducing carbohydrate intake usually means that people reduce refined sugars from their diet, which helps with weight loss. Many people also like eating a lot of protein and fats in their diet as they prefer these foods.

Due to the high protein intake, this diet can lead to high cholesterol levels and cardiovascular and renal disease risk. With very low carbohydrate intake, adherents often complain about a lack of energy/power, and it is a difficult diet for people to sustain long term.


The carnivore diet only includes meat, fish, and other animal foods like eggs and certain dairy products. It excludes all other foods, including fruits, vegetables, legumes, grains, nuts, and seeds.

It’s advantages and disadvantages are like the keto diet, but in addition, because there are no fruits, vegetables, legumes, grains, nuts, and seeds, it is virtually impossible to get enough fibre in the diet, which can cause constipation. In addition, this can lead to a higher risk of heart attacks, strokes, and kidney disease. The low dairy intake can also lead to osteoporosis.

Practical tip: For keto and carnivore diets, I recommend getting regular blood tests (6monthy) to assess their cholesterol/triglycerides and kidney function and to monitor blood pressure regularly. Like vegetarian/vegan, I would recommend people seek professional advice to ensure a balanced diet.

Comparing costs

Assessing what other foods need to be incorporated into each of the diets to ensure they are nutritionally balanced is vital. Some diets will require supplementation, which can be costly. Some diets may lead to health issues that require prescription medications, hospitalisations and medical treatments that can be very expensive.

When thinking about cost, I consider a variety of things:

  • The cost of the food itself
  • The cost of any additional food/supplementation required if the diet is not nutritionally adequate
  • Any medical treatments required because of the diet
  • Any prescription costs associated with the disadvantages of the diet

At certain times, healthy food can become increasingly expensive. After Cyclone Yasi hit Queensland in 2011, the price of bananas went from <$5/kg to $15/kg. In 2022 we have seen the impact of the recent floods and the War in Ukraine on the costs of some foods as their supply becomes limited, most recently, lettuce. But with all these things, it is usually the case of supply and demand, and once the crisis is averted, the prices drop back to normal. That’s what happened to bananas and lettuce, and that is what will happen with some food prices now.

With that said, I still rate the Mediterranean diet as the most cost effective, and I say that because this diet gives the best balance of all core food groups and leads to the most significant health benefits.  All the vitamins and minerals required are sourced from foods, and no supplementation is needed. This approach is widely studied and proven to show the most significant health benefits and having poor health can be costly.

Cook for yourself and feast on the benefits
Cook for yourself and feast on the benefits
Cook for yourself and feast on the benefits

Cooking for yourself gives you back control of your diet. You can choose your ingredients and your portion size and every input into the meal. When there is a temporary increase in price, you can look for alternatives. For the current crisis in the price of iceberg lettuce, substitute for cabbage. You get the same or better nutritional value and convenience but at a lower price.

As for comparing the prices of cooking for yourself at home or buying takeaway, there are some interesting studies you may want to be aware of:

  1. A 2017 New Zealand study compared six popular takeaway meals with making the same meal at home. Home-assembled meals are a better option than takeaway meals, as they are 15–48 % cheaper and have similar preparation/waiting times. 
  2. This is consistent with a TASTE magazine article that compared ($AUD per serve) of food preparation:

                                              Take away       Home Made

Pizza (1/2 pizza)                      6.50                    2.10

Fish and chips                            7.40                    3.20

Pad Thai                                      9.80                    2.00

Chicken Korma                          7.50                    3.40

  1. A 2009 Tasmanian study of 1277 men and 1586 women showed that people eating takeaway food at least twice a week were statistically less likely to meet the dietary recommendation for vegetables, fruit, dairy, extra nutrition, bread, and cereals (men only), lean meat and alternatives (women only) and overall met significantly fewer dietary recommendations.

In addition, after adjusting for confounding variables (age, leisure-time physical activity, TV viewing and employment status), consuming takeaway food twice a week or more was associated with a 31% higher prevalence of moderate abdominal obesity in men and a 25% higher prevalence in women.

So overall, takeaway food is not as nutritious and leads to weight gain.This can also result in the need for other medical costs in addition to the price of the food. But, you may ask, ‘what if I just buy unhealthy ingredients at the supermarket—you can procure junk food there as well’.

Tips on food shopping
  1. Never go shopping hungry – you buy more
  2. Always use a shopping list and stick to it
  3. Try to avoid impulse buys that “save you money”. Sometimes you save some cash, but it may cost your health in the long run.
  4. High volume areas are at the back of the store (dairy) and low volume in the corner (Vitamins). There are usually no healthy food options at the end of the aisles.
  5. Learn how to use a label to select products

There are so many factors that go into choosing the right diet, and so many competing ideologies, ‘influencers’ and brands spending big on marketing to encourage you to purchase their products.

It’s clear that a Mediterranean diet, or something similar to it, comes out on top in terms of balance and cost and well-being as well.


Peter ClarkPeter Clark is a PhD candidate at Griffith University and member of the Healthy Primary Care research team. An Advanced Accredited Practising Dietitian and Nutritionist, an Advanced Sports Dietitian (SDA), a Member of Academy of Nutrition and Dietetics (USA) and a Principal, Healthier You Pty. Ltd.


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