Altered Feeding Patterns in Rats Exposed to a Palatable Cafeteria Diet: Increased Snacking and its Implications for Developmental Obesity, Sarah Martire, Nathan Holmes, Fred Westbrook, Margaret Morris, PLOS One, April 2013|Volume 8|Issue 4| e60407.
“Rats prefer energy-rich foods over chow and eat them to excess. The pattern of eating elicited by this diet is unknown. We … compared the eating patterns of rats fed an energy rich cafeteria diet or chow.”
Twenty four Sprague Dawley rats (obtained from the Animal Resource Centre, Perth) were housed in plastic boxes (2 rats per box, measuring 22cm high, 65cm long, 40cm wide) in a climate-controlled environment (12 hour light/dark cycles). For one week, rats were fed a standard chow diet and handled daily. Following acclimatisation, they were randomly assigned a standard lab chow diet or a high fat cafeteria diet consisting of meat pies, Dim Sims, pasta, potato chips, oats, dog food roll, lamingtons and biscuits – as well as the standard chow.
Cafeteria fed rats ate more protein, fat and carbohydrate and consistently ingested double the energy of chow fed rats. The study classified a meal as consisting of an eating, grooming and sleeping cycle, whereas snacking was eating only. Researchers looked at the frequency of meals, snacks and the type of food eaten.
Given choice, rats will eat energy-rich food such as meat pies, lamingtons, biscuits, and Dim Sims in preference to standard chow. Cafeteria rats increased their weight up to the point of being 270 percent heavier after sixteen weeks on the diet, whereas the chow fed only rats had increased by 170 percent. The cafeteria rats ate more food and that food was more energy dense. They snacked more frequently in the early weeks but this slowed down as the study continued. The aim of the study was to determine what long-term effects on feeding patterns were brought about by a palatable diet.
The experimental protocol was approved by the Animal Care and Ethics Committee of the University of New South Wales and in accordance to the National Health and Medical Research Council, which provided a grant of $414,300.
- The authors state that this is the ‘First to record the eating patterns of rats free to consume the energy-rich foods eaten by people…’ But it’s not. The previous study by Rogers and Blundell, mentioned in this report, looked at the same scenario, but employed slightly different methods such as the criteria for ‘meal’ and ‘snack’, and the food on offer was only chow, white bread and chocolate. Apparently rats were more tempted by a greater variety of food such as Dim Sims and lamingtons. There is also a plethora of research that examines the eating patterns of adolescent humans. For example, ‘Snacking behaviours of adolescents and their association with skipping meals,’ (2007 Savige, Macfarlane, Ball, Worsley and Crawford) http://www.libnpa.org/content/4/1/36 . Also, ‘Dietary habits, food consumption, and nutrient intake during adolescence,’ (1992, Bull, Phil)
- The rats were housed in boxes. Was the boredom effect considered with regard to rat snacking? A study on humans, ‘You are what you eat: The effects of boredom on food consumption,’ found that bored participants ate differently to stimulated ones (2012, Johnson, Laporte, Choi Sze Pui). Unlike the rats in this study, humans live in all kinds of settings and eating is a social habit as well as a life supporting one. The process does not occur in a vacuum. Adolescents are particularly susceptible to peer and media influence, messages about obesity, fitting in, educational and socio-economic background and alcohol consumption patterns (Berger, 2011). As there is an abundant supply of overweight children, adolescents and adults there is no point to studying rats in this way and the study is not relevant as it does not mimic the human situation.
- Limitations of using animals to model humans that are relevant to this study include: ‘Loss of biological variability…inadequate group size; lack of co morbidities or other human risk factors; stress related physiological…distortions…interspecies variations (p75 Knight, 2011). Rats have a different caloric requirement to humans, needing fifty grams per kilogram per day of food compared to humans’ ten. They also have a dissimilar gastrointestinal pathway and metabolise, absorb and distribute food differently to humans (Knight, 2011).
- The study defined a meal for rats as those times when they ate, groomed and slept. Human habits are not so definite and people are more inclined to groom before a meal than after it, whilst sleeping is also variable. How can this parameter be compared to humans when there is not a clearly defining line that divides human snacking and mealtimes
This study is repetitive because many other researchers have explored the subject of eating patterns in humans. These researchers have observed the behaviour of a different species of animal, housed in an artificial environment, and this cannot be applied to the human situation. If we really need even more information on this subject, an effective alternative would be a large scale population study of humans’ eating patterns.
The only thing achieved here was that we now know at least twenty four bored rats preferred lamingtons, Dim Sims, biscuits and meat pies to commercial rat chow.
What can you do?
Contact the University of NSW Ethics Committee and ask how this waste of resources can be necessary to study human dietary habits.
University of New South Wales Animal Ethics Committee
Office of the Deputy Vice-Chancellor (Research)
University of New South Wales
Ask the NHMRC how they can justify wasting $414,300 of taxpayer dollars on such useless and unnecessary “research”.
NHRMC, GPO Box 142
Canberra ACT 2601
Berger, K. (2011). The Developing Person Through the Lifespan . New York: Worth.
Knight, A. (2011). The Costs and Benefits of Animal Experiments. United Kingdom: Palgrave Macmillan.