Human Appetite Research - Working Towards Effective Dietary Strategies For Weight Loss

Published on 17 April 2009 in Food, health and wellbeing

Dr Alex Johnstone in the Human Nutrition Unit


Awareness of the obesity epidemic in Scotland and the associated co-morbidities of type II diabetes and cardiovascular disorders has focused attention on developing novel effective strategies to reduce caloric intake. One of the main reasons dieters fail to succeed is because they feel hungry. Diet composition strongly affects energy intake, and human studies highlight protein as a more satiating macronutrient than either carbohydrate or fat. This means that it promotes a feeling of fullness. This has led to development of a number of weight-reducing diets based on high protein intakes with satiety reached and hunger satisfied at caloric intakes below normal daily energy expenditure requirements, leading to weight loss. Our research is investigating the role of nutrition and diet composition in controlling hunger and appetite or 'motivation to eat'. Eating is a form of behaviour and we try to understand what influences it, and also the underlying physiology. Our aim is to develop novel strategies that will help achieve weight loss and improve health.

Key Points

This research is investigating how to develop diets that satisfy hunger at caloric intakes below daily energy requirements to achieve weight loss. It is possible to lose weight and not feel hungry.

Our diet trials in obese men highlight that a small weight loss (e.g. 4kg or 8lb) over a couple of weeks, can improve health, for example, as indicated by positive changes in lowering blood pressure, lowering cholesterol or improving glycaemic control (blood glucose)

We are investigating the impact of different nutritional weight loss regimes on health. For example, current work is examining vegetarian weight loss diets using soya protein and their effect on metabolic health and indices of gut health.

We are attempting to understand the underlying physiology controlling appetite and linking this to behaviour. This is complicated by the fact that hunger and appetite are influenced by psychological and physiological factors. We call these ‘hedonic’ and ‘energostatic’ drivers.

Research Undertaken

 What research have we carried out on this topic ?
We have conducted dietary human intervention studies within the Human Nutrition Unit at the University of Aberdeen Rowett Institute of Nutrition and Health to assess:
  • How altering the nutritional content of the diet affects hunger, food intake and bodyweight in obese subjects.
  •  The impact of dietary protein and carbohydrate on appetite control in the brain using Positron Emission Tomography scan technology to look at metabolism in the brain.
  •  What factors influence satiety and promote weight loss to improve metabolic health.
What are the key findings of this research ?
Eat what you want and not feel hungry and still lose weight is the ultimate aim of dieting.

This research has highlighted that:
  • High protein weight loss diets promote reduced energy intake. The underlying physiological mechanisms for this are still unclear but are likely to involve gut-brain interactions. Future work will focus on this aspect.
  •  A low-carbohydrate, high-protein diet invokes satiety, reduced energy intake and weight loss, and this is likely to be linked, in part, to ketosis induced anorexia. (This is when the body uses ketone bodies as a fuel for the brain).
  •  Altering diet composition of weight loss diets can impact on satiety within the frontal cortex of the brain, as indicated by Positron Emission Tomography scans.
  •  Types of protein may be important and we will assess how meat based and vegetarian diets impact on motivation to eat.

Policy Implications

This science directly targets the role of diet composition in our ‘obesegenic environment’.
Public health nutrition advice on weight loss for policy makers and advisors needs to be evidence-based, which this work provides.
The research is based on ethical-decision making principles that can be translated to public health nutrition colleagues, for example, in the NHS.
Policy formulation for effective practice and intervention is conducted as a multi-disciplinary team, where the role of food and nutrition must be a key factor.
Social marketing of health-related advice to Scottish consumers should be based on scientific fact. This work shows evidence of a dietary based strategy that tackles appetite control.


Dr Alexandra Johnstone


Food, health and wellbeing

Comments or Questions

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A very interesting report.

Posted on 22 April 2009 by margaretfuery