Certain diets are designed to meet certain goals. For example diets are designed to aid in controlling hypertension, to cause fat loss, to maintain weight etc.
More or less these goals pertain to a particular health condition and it seems acceptable to think of certain foods to help in a particular condition.
But that is not where it ends. Surprisingly we are now shifting to an era where diets are designed to activate certain genes! I never thought that would be possible but it exists. It is called Sirtfood diet.
What is sirtuin and how is it linked with calorie restriction?
Sirtuin are a group of genes that are involved in regulation of life span of organisms. These are housekeeping genes. In other words they are responsible for repair and maintenance of cells.
In mammals they are 7 of them: SIRT1-7. They regulate cellular energy, cell death, aging, inflammation etc.
McCay et al were the first to demonstrate that calorie restriction (restricting intake by 60-70% of the regular calorie intake) extends life of rodents. Similar findings were reported in a number of species including primates.
One of the most important finding in these studies was the association of increased sirtuins and extension of lifespan due to calorie restriction. Therefore activation of sirtuin is associated with longevity and thought to be a secret to the ‘fountain of youth’.
SIRT1 is also known as ‘skinny gene’ as it regulates fat storage and metabolism.
Scientists then started looking for dietary elements that could activate sirtuin. That is how Sirtfoods were identified. It is felt that these foods mimic the activity of fasting, calorie restriction and exercise and thus can speed up weight loss and promote health.
What is Sirtfood diet?
The Sirtfood diet was developed by nutritionists: Aidan Goggins and Glen Matten. The idea behind this diet was to include foods that activate sirtuin in order to promote health and longevity.
Additionally these foods mimic the effect of calorie restriction, so weight loss is a sure shot outcome.
The diet consists of the following phases:
In this phase, severe calorie restriction is observed. For days 0 to 3, the goal is of 1000 calories which is made up of 3 Sirtfood rich green juices and 1 meal rich in Sirtfoods.
Days 4 to 7, calorie intake is increased to 1500 calories and for this 2 Sirtfood rich juice and 2 Sirtfood rich meals are to be consumed.
The first phase is considered as a detox phase which initiates autophagy- clearing of old cell debris and paves the way for fat burning.
This consists of a 14 day maintenance phase where no calorie restriction is involved and weight loss is said to occur on autopilot. However meals consumed are to be rich in Sirtfoods and a ‘maintenance’ Sirtfood juice is to be consumed.
The authors state that this is not a typical diet where you restrict a certain item. In fact just increasing the amount of Sirtfoods in your diet will help you lose weight.
What are ‘Sirtfoods’?
Antioxidants found in plants (polyphenols) are potent activators of sirtuin and offer great protection against number of diseases.
In their book ‘The Sirtfood diet’, authors have mentioned a number of Sirtfoods which form the basis of this diet. Here are a few of them:
Sirtuin activating ingredient
|Coffee||Caffeic acid, Chlorogenic acid|
|Red wine||Resveratrol, Piceatannol|
|Green tea||Epigallocatechin gallate|
|Extra virgin olive oil||Hydroxytyrosol, Oleuropein|
What does research have to say about role of Sirtfood diet in weight loss?
Sirtfood diet is power packed with highly nutritious foods and this could be one reason why it should be given a thumbs up. But sadly there are no scientific studies specifically on this diet and its effect on body weight and health.
The Sirtfood Pilot study
The authors of Sirtfood diet conducted a study to test the effect of Sirtfood diet. This study has been mentioned in detail in their book- ‘The Sirtfood diet’. It was carried out in KX, London’s popular health and fitness centre.
The study population consisted of healthy individuals who indulged in regular exercise in order to set a minimum benchmark. Two individuals in this group were overweight. Weight, body composition and metabolic parameters were recorded.
The study lasted for 7 days and was completed by 39 out of 40 participants. Average weight loss was 7 pounds in 7 days. Muscle mass was not lost, rather maintained or increased. Participants rarely felt hungry. In fact they felt energetic and appeared healthy.
7 pounds (3.2kg) in 7 days is astonishing. Another important feature is that muscle mass is maintained. In other words, Sirtfoods burn fat and maintain and repair muscle. More muscle means higher energy expenditure even while resting. So with Sirtfoods you burn fat with minimal drop in metabolism.
What does this mean?
A pilot study on Sirtfood diet reported excellent results- 7 pound weight loss in 7 days. Muscle mass was also maintained.
Dietary activators of sirtuin
In their paper ‘Dietary Activators of Sirt1’, Allard et al discuss how activation of sirtuin extends lifespan in several species ranging from yeast to dogs. They mention how caffeine and omega 3 fatty acids increase lifespan and increase expression of sirtuin.
The principal dietary activator, according to them, is resveratrol. This compound is present in the skin of grapes and the authors have collected a number of studies that show resveratrol increases expression of sirtuin.
What does this mean?
Research shows that antioxidants present in plants can activate sirtuin. Few such compounds include resveratrol, curcumin and green tea catechins.
Implications of sirtuin on obesity
Sirtuin 1 regulates cellular metabolism. Research shows that sirtuin1 regulates glucose and fat metabolism, promotes mobilization of fat, controls insulin secretion of pancreas and affects obesity induced inflammation.
Increased expression of Sirtuin 1 leads to decreased fat storage and increased break down of fats. Reduction in fat tissue is proven to increase lifespan in mice. It is thought that drugs or agents that activate sirtuin1 gene act as calorie restriction mimetics by increasing fat mobilization.
Research shows that mice deficient in sirtuin 3 develop obesity, insulin resistance and features of metabolic syndrome when fed a high fat, calorie dense diet. This suggests that activation of sirtuin 3 can serve to be therapeutic in controlling obesity and related condition.
Despite of these findings in animal studies, there is no direct evidence in terms of clinical trials on humans that direct activation of sirtuin leads to weight loss. There is much debate whether these studies proven in test tubes can be proven in humans too.
What does this mean?
Sirtuin is proven to regulate fat storage and metabolism but whether this can be exploited or used as a therapeutic target in real life is still a matter of debate.
Clinical trials on Sirtfood concept
After a rigorous search I came across two clinical trials related to this entire concept of Sirtfood and calorie restriction.
The first study investigated the effect of calorie restriction on sirtuin levels in obese individuals. 4 participants were treated with 25% calorie restriction for 7 weeks. Body weight, BMI, fat mass all decreased and interestingly sirtuin1 expression increased.
Researchers concluded that calorie restriction has positive effects on obesity related conditions and this occurs probably due to activation of sirtuin.
Another study showed that resveratrol works as a calorie restriction mimetic in obese humans by bringing about improvement in metabolic parameters. However no changes in body weight were reported.
What does this mean?
Calorie restriction is found to increase sirtuin levels in obese individuals which suggests that agents that mimic calorie restriction can aid in weight loss and improving health. However stronger clinical trials are required to prove this.
Sirtfood diet has some really promising health foods under its wing but the lack of scientific evidence makes it difficult to recommend this diet for weight loss.
However I will not refrain from suggesting including Sirtfoods in your diet as when possible. After all what is the harm in including low calorie, super healthy foods.