Thermic Effects of Some Scottish Plant Foods
Condition: Diet Induced Thermogenesis; Obesity Control
MeSH terms: Obesity
Study type: Interventional

Summary: 
      Weight gain occurs because of imbalances in energy balance favouring energy intake. Whilst
      over 50% of a person's energy requirement goes towards the maintenance of physiological
      functions, around 40% is used for physical activity. In addition to this, around 10-15% of
      energy is spent on what is termed as Diet Induced Thermogenesis (DIT). Diet Induced
      Thermogenesis is the increase in energy expenditure following a meal, and represents the
      energy utilised for the digestion and metabolism of food. Some nutrients such as proteins
      require more energy to digest and therefore produce a greater DIT than others. In addition to
      this, some food components are able to independently stimulate calorie burning. For example
      caffeine, chilli, ginger and green tea have been shown to induce calorie burning through DIT.
      Therefore the inclusion of such foods in the diet could increase energy expenditure and
      thereby help in weight control.

      The objective of this study is to determine the DIT effects of some plant foods that are
      native to Scotland (blackberries, blueberries, red raspberries, wild garlic and sea
      buckthorn). These foods have been shown to contain compounds that stimulate DIT. If found to
      be effective, these foods could then be used to develop dietary strategies for weight control
      in Scotland.
    

Detailed description: 
      Obesity prevalence is increasing around the world and the United Kingdom is no exception.
      Latest statistics show that approximately 25% of the UK population is obese and is predicted
      to rise to 70% by 2020 if present trends continue. Obesity is particularly widespread in
      Scotland where approximately 62% of the population are of a BMI over 25kg/m2. Curtailing
      obesity rates is a public health priority as excess weight is also the greatest predictor of
      other co-morbidities such as cardiovascular disease, cancer and diabetes, and hence
      collectively exerts a significant toll on the health and economic burden of the country.

      Weight gain occurs primarily due to an imbalance in energy balance status where energy intake
      outweighs expenditure. Energy expenditure (EE) in adults consists of three components: basal
      metabolism (50-70% of EE), physical activity (30-40% of EE) and diet induced thermogenesis
      (DIT). The latter is described as the thermic effect of food and is the increase in EE above
      Basal Metabolic Rate after a meal, and usually ranges between 3-10% of total EE (depending on
      the composition of the meal). Whilst cornerstone approaches to weight control have focused on
      strategies to reduce energy intake and increase physical activity, the still escalating
      obesity levels show that this approach is ineffective in the long term possibly due to poor
      long-term compliance to dietary regimes and adequate physical activity. Thus it is being
      increasingly recognised that the most sustainable long-term strategy for reducing obesity is
      making small diet and lifestyle changes that would positively influence energy regulatory
      mechanisms targeted at preventing a positive energy balance. It is also now recognised that
      genetic predispositions to a slow mechanism characterised by a slow metabolic rate and
      capacity for fat oxidation also determines an individual's propensity to weight gain.
      Furthermore, studies have shown that weight loss and reduced food intake result in an
      attenuation of EE possibly due to the loss of lean mass and improved metabolic efficiency.
      The regular consumption of high DIT foods which could increase EE and fat oxidation whilst
      circumventing these energy sparing mechanisms may have significant potential in long-term
      weight control. Indeed studies demonstrating pronounced obesity in mice whose DIT mechanism
      were inactivated indicates the important role thermogenesis plays in weight control

      Food components such as chilli (capsaicin), ginger, mustard, pepper, caffeine, green tea
      (flavanols) and medium-chain triglycerides have been demonstrated as increasing DIT. The
      thermogenic effects of these compounds have been shown to be mainly via the sympathetic
      nervous system. Pharmacological agents such as ephedrine and salicylate as well as food
      constituents such as methylxanthines (theophylline and caffeine) and caffeine have been shown
      to possess sympathomimetic properties and induce fat oxidation and thermogenesis in effector
      cells by stimulating the release of noradrenalin. Flavanoids such as green tea catechins have
      also been shown to stimulate this pathway. Sympathetically released noradrenalin has been
      shown to activate Beta3adrenoceptors and thereby induce thermogenesis and fat oxidation in
      peripheral tissues as well as activate uncoupling protein (UCP1) that mediates thermogenesis
      in brown adipose tissue (BAT). Plant phenolics have also been shown to demonstrate
      thermogenic effects, particularly Oleuropein, green tea catechins, Kaempferol, flavanol
      glycosides, stilbenes and quercetin.

      The objective of the present pilot study is to assess the thermogenic effects of some plant
      foods native to Scotland that contain the above phytochemicals. Specifically, the study will
      investigate the thermogenic effects of berries (blackberries [Rubus sp.], blueberries
      [Vaccinium corymbosum] and red raspberries [Rubus idaeus L]), wild garlic (Allium ursinum)
      and sea buckthorn (Hippophae rhamnoides). Blackberries, blueberries and raspberries have been
      shown to be rich in flavonoids and phenolics including catechins and raspberry ketones which
      have been suggested to be thermogenic. These berries are also rich in anthocyanins such as
      cyanidin-3-glucoside which has been shown to potentially promote thermogenesis by
      upregulating UCP1. Furthermore, blueberries have been shown to be a good source of stilbenes
      such as resveratrol and pterostilbene which have demonstrated thermic effects elsewhere.
      Similarly, sea buckthorn has been reported to contain catechins, epicatechins and flavonols
      such as isorhamnetin, quercetin and kaempferol. Sea buckthorn is also rich in carotenoids,
      especially those with provitamin A activity that have been shown to upregulate the expression
      of UCP1 and thereby influence thermogenesis. Wild garlic contains Sulphur containing
      compounds such as alliin and Allicin derivatives (diallyldisulphide) that in studies using
      garlic have shown thermogenic activity by enhancing noradrenalin secretion and stimulating
      brown adipose tissue. Indeed the total thiosulfinate content in wild garlic has been shown to
      be comparable to garlic.

      The presence of thermogenic compounds in these plant products logically suggests that they
      may have a thermic effect in humans and this forms the rationale for the present study. No
      studies have investigated the thermic effects of these foods in humans and their therapeutic
      potential in weight control from a thermogenesis perspective. The proposed pilot study will
      provide preliminary data on the thermic effects of these Scottish foods and provide a basis
      for future research.
    

Intervention name(s): Control Meal; Berry Treatment; Sea Buckthorn Treatment; Wild Garlic Treatment
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): This will consist of standard breakfast foods (cereal, milk, yoghurt, cheese cracker bread, butter, banana and cream; This will consist of standard breakfast foods (cereal, milk, yoghurt, cheese cracker bread, butter, banana and cream plus a berry smoothie. The berry smoothie consists of blueberries, raspberries and blackberries.; This will consist of standard breakfast foods (cereal, milk, yoghurt, cheese cracker bread, butter, banana and cream plus a sea buckthorn berry smoothie.; This will consist of standard breakfast foods (cereal, milk, yoghurt, cheese cracker bread, butter, banana and cream. The wild garlic will be prepared and served as a dip alongside.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Health Services Research
Keywords: Diet Induced Thermogenesis; Obesity; Energy balance; Energy expenditure; berries; Sea Buckthorn; Wild garlic