A Ketogenic Diet and Weight Loss. More Harm than Good?

This blog is written by our clinicians and aims to keep patients informed with up to date information on medical conditions. The editor of the blog is Dr Cristina Romete.

What is a ketogenic diet

A ketogenic diet (KD) is very low in carbohydrates, provides adequate protein, and supplies most of its calories in the form of fats.

As fat is the main source of energy being consumed, the body must then use this (i.e. break it down) as the main source of ‘fuel’. When fat is metabolised for energy, by-products called ketone bodies (molecules that are made by the liver from fatty acids) are produced which are used up by the body’s tissues, muscles and the brain. This process is known as ketosis.

How do you lose weight during a ketogenic diet

The body can enter ketosis during times of severe energy restriction (such as during starvation) or prolonged intense exercise, or when carbohydrate intake is reduced to approximately 50g a day or less as in the ketogenic diet.

This reduction in carbohydrates not only restricts the intake of starchy food such as bread, pasta, rice, and cereal but also limits dairy products, beans and pulses, fruit and vegetables….and the list goes on! Furthermore, fruit and vegetables are, however, an excellent source of vitamins, minerals, dietary fibre and phytochemicals, which are linked with a range of functions in the body, including gut health and immunity. We all know the target for eating fruit and vegetables is at least five-a-day, but with an intake of less than 50g of carbohydrates per day this makes achieving this target difficult and puts a restriction on which types can be consumed. Therefore, achieving a well-balanced diet is very challenging and supplementation with vitamins and minerals would be required.

Research supports a role for the Ketogenic diet as a medical intervention for some cases of epilepsy, particularly in children and it has been used as treatment in this condition since the 1920s. However, the popularity of this diet in aiding weight loss has become a growing trend recently. You only need to type ‘#keto’ to see its popularity on social media. However, due to the restrictive nature of this diet and complexity of medical conditions such as epilepsy, the full support of a multidisciplinary medical team, including doctors, dietitians, nurses, and pharmacists are needed. Unfortunately many individuals with little nutrition education advocate and promote this diet as the next best thing to help lose weight. This is a concern amongst Health Care Professionals that have to deal with the complications of individuals who are provided with at best incorrect and at worst dangerous information.

Following a ketogenic diet will most likely result in short-term weight loss (as do many diets), which probably results due to a reduction in total energy (kcal) intake, the depletion of glycogen stores and associated water, and a reduced appetite, and also due to satiety (associated with eating high fat and protein foods).

What is the best approach to dieting

Though the ketogenic diet may offer some metabolic benefits when followed in the short-term (a few months), and be recommended as treatment for certain medical conditions, the key to maintaining a healthy weight in the long-term is an eating pattern that is sustainable over time. Moreover, a healthy relationship with food is imperative and the restrictive nature of this diet can, for example, lead to avoidance of social events due to difficulty eating suitable foods when out and about.

The avoidance of whole food groups and limitation of others can lead to nutritional deficiencies which in turn can result in a number of health concerns. A number of studies have reported a high dropout rate of participants following this diet namely because of its restrictive nature which makes understanding the long-term implications difficult.

Short-term side effects of ketosis can include fatigue, bad breath, constipation, nausea and headache. With the restriction of carbohydrates also comes with the reduction in dietary fibre which can cause constipation. Research supports the protective effect of dietary fibre in a number of medical conditions and a high intake of dietary fibre, in particular, cereal fibre and whole grains, has been associated with a reduced risk of colorectal cancer. The fibre in whole grains, fruit, vegetables, and legumes also supports the growth of ‘good’ bacteria, which keeps the lining of the bowel healthy.  In the UK most people do not eat enough dietary fibre (the average intake is 17.2/day for women and 20.1g/day for men) and the recommended intake per day is 30g per day. This means following a ketogenic diet will, unfortunately, make achieving this target more difficult.

The ketogenic diet does have some potential benefits and may be of use in those for example that require to lose weight prior to undergoing surgery. However, as this is a specialised diet it is important to seek advice from a qualified Health Care Professional as this diet may do more harm than good.

For further information, or if you wish to make an appointment with our Dietitian Laura Court, please contact us on the number below.

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