What’s in the web for family physicians - exploring the trendy diet types and their health implications

Sio-pan Chan 陳少斌，Wilbert WB Wong 王維斌，Alfred KY Tang 鄧權恩

“You are what you eat”, is a well-known saying that emphasises the importance of healthy eating habits. This statement implies that the food we consume directly affects our physical and mental well-being. Similarly, traditional Chinese medicine is also paying much attention to one’s diet and often uses diet as part of the treatment (膳療). The typical so-called Western diet is well-known to be the root cause of many metabolic diseases such as hypertension, diabetes, obesity and metabolic syndrome, etc. Despite the importance of diet in influencing our health, very little time is spent on any medical curriculum on diet and nutrition. In fact, nutrition was not even mentioned in the curriculum of both the University of Hong Kong or Chinese University of Hong Kong. A typical medical student in the United Kingdom receives a 2-hour lecture on nutrition in second year and another 1-hour lecture on obesity management. As most curricula are disease orientated, students are taught to focus on diseases rather than on health keeping. As a matter of fact, the food pyramid is still recommended on the website of The Centre for Health Protection as healthy diet choice. This classical food pyramid itself was, surprisingly, not introduced by any health authority, but by the United State Department of Agriculture. The food pyramid was subjected to much criticism in recent years. The main limitations of the food pyramid include:

1. Oversimplification: it oversimplifies dietary recommendations by grouping foods into broad categories without considering the variety within them. It fails to differentiate between healthy and unhealthy options within each food group, e.g. fresh meat is nutritionally much healthier than processed meat even if they may have similar caloric value.


2. Influence from food industry: the influence of the food industry played a role in the development of the food pyramid. Some believe that it prioritised the interests of the agricultural sector rather than focusing solely on public health.


3. Carbohydrate emphasis: The original food pyramid placed a heavy emphasis on carbohydrates, particularly grains, suggesting a high-carbohydrate, low-fat diet. In recent years, there is an increasing amount of evidence that points to the fact that too much carbohydrates, especially in the form of simple sugars, is harmful to health.


4. “A calorie is a calorie”, the old thermodynamic concept of how many calories intake equals to what we actually get is outdated. We now know the gut microbiome has a huge influence on how much energy we actually get from the food eaten. The gut microbiome can digest supposedly indigestible fibres to be returned to us in the form of shortchain fatty acids (SCFAs), etc.

In the era of social media, we often come across many diet types which are recommended for various purposes, the most famous diet must be the Atkins diet which claims to work miracles for weight control. Other better known diets include the Mediterranean, vegan, paleo, low carb, ketogenic diet and intermittent fasting. Most of them claims to have beneficial effects on health. We shall present a review on the pros and cons of the more popular types of diet with what we can find on the internet.

Atkins diet and ketogenic diet

The Atkins diet is a low-carb, high-protein diet that was developed by the cardiologist Dr. Robert Atkins in the 1960s. The diet focuses on reducing the intake of carbohydrates including sugars, grains, and starchy vegetables, while increasing the consumption of protein and “healthy” fats. The Atkins diet can give rapid weight loss, especially during the initial period of the program. Restricting carbohydrate would force the body to burn stored fat for energy consumption, resulting in weight loss. By limiting carbohydrates intake, the Atkins diet can help to stabilise blood sugar levels, making it beneficial to individuals with diabetes or insulin resistance. Studies have also shown that the Atkins diet can lead to a reduction in triglyceride levels, increased levels of high-density lipoprotein cholesterol, and improved markers of heart health. High-protein foods and fats, which are the essence of the Atkins diet, can help to improve satiety and reduce cravings, leading to a better control of appetite.

The cons are, the individual is constantly in a state of ketosis, some individuals may experience symptoms such as bad breath, fatigue, constipation, or headaches. In severe cases, this can lead to ketoacidosis, a potentially dangerous condition, especially in patients with diabetes. A strict reduction of carbohydrate intake can lead to insufficient intake of certain essential nutrients like fibres, vitamins, and minerals, which are mainly found in carbohydrate-rich foods. Moreover, the highly restrictive nature of the Atkins diet may make it difficult to keep it sustainable. As for Dr. Atkin himself, he was known to suffer from coronary heart disease himself and he weighed a massive 117 kg at the time of his death.

Ketogenic diet differs from Atkins diet by allowing a slightly higher carbohydrate intake. Both diets work by inducing the body into a ketosis state, the body then uses ketones instead of glucose for energy supply, so essentially the fat becomes the primary source of energy. The pros and cons are essentially the same as the Atkins diet. However, a modified Atkins diet that induces ketosis can be very useful in treating paediatric intractable epilepsy.

Intermittent fasting

Instead of focusing on what to eat, Intermittent fasting is about when you eat.

Intermittent fasting is an eating pattern that involves alternating periods of fasting and eating. It has gained popularity for its potential health benefits. There are many different ways to do intermittent fasting, by reducing calorie intake, intermittent fasting can help promote weight loss, fat loss, help preserve lean muscle mass and improve body composition. Intermittent fasting can enhance insulin sensitivity, which may help regulate blood sugar levels and reduce the risk of type 2 diabetes. Fasting triggers cellular processes like autophagy, which is the bodyʼs way of cleaning out damaged cells and recycling cellular components. This may have anti-aging and diseasefighting benefits. The 16:8 intermittent fasting plan is getting more and more popular in recent years. It involves consuming foods during an 8-hour window and fasting for the remaining 16 hours each day. Most people following this 16:8 plan abstain from food after dinner in the evening and at night and for part of the morning. They limit their daily calories intake to the middle of the day. This flexibility makes the plan relatively easy to follow. Some research suggests this is useful for weight loss in the short term because people end up eating less. Itʼs long-term usefulness needs further evaluation.

Contraindications to intermittent fasting includes children less than 18 years of age, those with type I diabetes, history of eating disorder. Without proper planning, intermittent fasting can lead to inadequate intake of essential nutrients. During eating windows, a well-balanced diet is to be followed to meet nutritional needs. Intermittent fasting may not be good for everyone. Some people may experience side effects such as fatigue, dizziness, irritability, or difficulty concentrating during fasting periods. These symptoms can vary according to pre-existing health conditions and should be monitored closely.

Mediterranean diet

The Mediterranean diet is characterised by a high consumption of fruits, vegetables, whole grains, legumes, nuts, and olive oil, with moderate amounts of fish, poultry, dairy, and red wine, and limited intake of red meat and processed foods. This diet has been associated with numerous health benefits. Studies have shown that the Mediterranean diet is associated with a reduced risk of heart disease. It also lowers the levels of low-density lipoprotein cholesterol, blood pressure, and inflammation. The Mediterranean diet has been linked to a lower risk of cognitive decline, dementia, and Alzheimer's disease. It can also improve blood sugar control and insulin sensitivity. Some studies have found that the Mediterranean diet is associated with a lower risk of certain types of cancer, such as breast and colorectal cancer, possibly due to its high antioxidant and anti-inflammatory properties. However, individuals with lactose intolerance or nut allergies may need to modify or avoid certain components of the diet. The Mediterranean diet may not provide adequate amounts of certain nutrients such as calcium, iron, and vitamin D, which are primarily found in dairy and fortified foods.

The Palaeolithic (Paleo) diet

The Palaeolithic diet, also known as the Paleo diet or the Caveman diet, is a popular dietary approach that tries to mimic the eating habits of our ancient ancestors during the Palaeolithic era. The diet primarily focuses on consuming foods that were available to huntergatherer societies, such as lean meats, fruits, vegetables, nuts, and seeds. It excludes processed foods, grains, legumes, dairy products, and added sugars.

Small scale studies have shown that the diet can help to improve blood sugar control, lower cholesterol levels, and reduce inflammation. However, there is also evidence that the diet can be too restrictive and difficult to follow, and that it may not be suitable for everyone. At the same time, the diet can be low in certain nutrients, such as calcium, iron, and vitamin D. Overall, the Palaeolithic diet is a controversial fad diet that has both pros and cons. In real life, it is both expensive and difficult to sustain.

Vegetarian and vegan diets

Vegetarian diets do not contain meat, poultry or fish; vegan diets further exclude dairy products and eggs. Vegetarian and vegan diets can vary widely, but the empirical evidence largely relates to the nutritional content and health effects of the average diet of welleducated vegetarians living in Western countries, together with some information on vegetarians in non- Western countries. In general, vegetarian diets provide relatively large amounts of cereals, pulses, nuts, fruits and vegetables. In terms of nutrients, vegetarian diets are usually rich in carbohydrates, n−6 fatty acids, dietary fibre, carotenoids, folic acid, vitamin C, vitamin E and Magnesium, and relatively low in protein, saturated fat, long-chain n−3 fatty acids, retinol, vitamin B12 and Zinc; vegans may have particularly low intakes of vitamin B12 and low intakes of Calcium. Cross-sectional studies of vegetarians and vegans have shown that, on average, they have a relatively low body mass index and a low plasma cholesterol concentration; recent studies have also shown higher plasma homocysteine concentrations than in non-vegetarians. Cohort studies of vegetarians have shown a moderate reduction in mortality from ischaemic heart disease but little difference in other major causes of death or allcause mortality in comparison with health-conscious non-vegetarians from the same population. Studies of cancer have not shown clear differences in cancer rates between vegetarians and non-vegetarians. More evidence is needed, particularly on the health of vegans and on the possible impacts on health of low intakes of long-chain n−3 fatty acids and vitamin B12. Overall, the data suggest that the health of Western vegetarians is good and similar to that of comparable non-vegetarians.

It is important to get all of the nutrients that one needs, such as protein, iron, calcium, and vitamin B12. Plant-based protein sources may not be as complete as animal-based ones, making it important to combine different plant foods to obtain all the essential amino acids. Vegan diets are typically organic and much more expensive than ordinary vegetarian food consumed in developing countries.