title: The snacking rat as model of human obesity: effects of a free-choice high-fat high-sugar diet on meal patterns.
abstract: OBJECTIVE
  Rats subjected to a free-choice high-fat high-sugar (fcHFHS) diet persistently overeat, exhibit increased food-motivated behavior and become overtly obese. Conversely, several studies using a non-choice (nc) high-energy diet showed only an initial increase in food intake with unaltered or reduced food-motivated behavior. This raises the question of the importance of choice in the persistence of hyperphagia in rats on a fcHFHS diet.
  
  
  METHODS
  Meal patterns, food intake and body weight gain were studied in male Wistar rats on free-choice diets with fat and/or sugar and in rats on nc diets with fat and sugar (custom made with ingredients similar to the fcHFHS diet).
  
  
  RESULTS
  Rats on a ncHFHS diet initially overconsumed, but reduced intake thereafter, whereas rats on a fcHFHS diet remained hyperphagic. Because half of the sugar intake in the fcHFHS group occurred during the inactive period, we next determined whether sugar intake during the light phase was a necessary requirement for hyperphagia, by restricting access to liquid sugar to either the light or dark period with unlimited access to fat and chow. Results showed that hyperphagia occurred irrespective of the timing of sugar intake. Meal pattern analysis revealed consumption of larger but fewer meals in the ncHFHS group, as well as the fcHF group. Interestingly, meal number was increased in all rats drinking liquid sugar (whether on a fcHFHS or a fcHS diet), whereas a compensatory decrease in meal size was only observed in the fcHS group, but not the fcHFHS group.
  
  
  CONCLUSIONS
  We hereby show the importance of choice in the observation of fcHFHS diet-induced hyperphagia, which results in increases in meal number due to sugar drinking without any compensatory decrease in meal size. We thus provide a novel dietary model in rats that mimics important features of human overconsumption that have been ignored in rodent models of obesity.
authors: Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors: S E
authors: 0000000242987451
authors: SE
authors: la Fleur
authors: Department of Neuroscience and Pharmacology, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors: M C M
authors: MC
authors: Luijendijk
authors: Department of Neuroscience and Pharmacology, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors: E M
authors: EM
authors: van der Zwaal
authors: Department of Neuroscience and Pharmacology, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors: M A D
authors: MA
authors: Brans
authors: Department of Neuroscience and Pharmacology, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors: R A H
authors: RA
authors: Adan
mesh_terms: D000818:Animals; D001835:Body Weight; D002755:Choice Behavior; D004041:Dietary Fats; D019422:Dietary Sucrose; D004195:Disease Models, Animal; D004435:Eating; D002149:Energy Intake; D005247:Feeding Behavior; D006963:Hyperphagia / Q000097:blood / Q000473:pathology*; D008297:Male; D009765:Obesity / Q000097:blood / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar; D062410:Snacks; D015430:Weight Gain
chemical_list: D004041:Dietary Fats; D019422:Dietary Sucrose
references: Int J Obes (Lond). 2007 Aug;31(8):1286-94
references: 17325683
references: Pharmacol Biochem Behav. 2010 Nov;97(1):130-7
references: 20478328
references: Chronobiol Int. 2011 Apr;28(3):216-28
references: 21452917
references: Int J Obes (Lond). 2010 Mar;34(3):537-46
references: 20029382
references: Int J Obes (Lond). 2011 Apr;35(4):595-604
references: 20714332
references: Appetite. 2009 Feb;52(1):21-6
references: 18694791
references: PLoS One. 2013;8(4):e60407
references: 23565243
references: Obesity (Silver Spring). 2010 May;18(5):966-70
references: 20150901
references: Physiol Behav. 2004 Sep 30;82(4):671-7
references: 15327915
references: Appetite. 2010 Dec;55(3):420-5
references: 20678532
references: Eur J Pharmacol. 2011 Jun 11;660(1):207-12
references: 21211524
references: Physiol Behav. 2003 Nov;80(2-3):253-8
references: 14637223
references: Obesity (Silver Spring). 2007 Apr;15(4):798-808
references: 17426312
references: J Nutr. 2011 Jan;141(1):158-62
references: 21123465
references: Obes Surg. 2009 Oct;19(10):1430-8
references: 19506986
references: Am J Physiol. 1998 Nov;275(5):R1511-22
references: 9791068
references: Eur J Neurosci. 2013 Apr;37(8):1350-6
references: 23331763
references: Am J Physiol Regul Integr Comp Physiol. 2011 Nov;301(5):R1267-80
references: 21849633
references: Obes Res. 2003 Jul;11(7):845-51
references: 12855753
references: Behav Neurosci. 2008 Dec;122(6):1257-63
references: 19045945
references: Am J Physiol Regul Integr Comp Physiol. 2000 Jan;278(1):R196-200
references: 10644639
references: J Nutr. 2003 Apr;133(4):1081-7
references: 12672923
references: Curr Opin Clin Nutr Metab Care. 2011 Jul;14(4):385-90
references: 21519237
references: Int J Obes (Lond). 2005 Jun;29(6):711-9
references: 15809664
references: Am J Physiol Regul Integr Comp Physiol. 2005 Jun;288(6):R1450-67
references: 15637168
references: J Neurosci. 2007 Dec 19;27(51):14139-46
references: 18094253
references: Physiol Behav. 2012 Jan 18;105(2):325-31
references: 21893075
references: Am J Clin Nutr. 2012 Apr;95(4):989-94
references: 22434603
references: Cell Metab. 2007 Nov;6(5):414-21
references: 17983587
references: Methods Mol Biol. 2012;829:351-65
references: 22231826
references: Neuroscience. 2003;122(1):17-20
references: 14596845
references: Eur J Pharmacol. 2008 May 6;585(1):31-7
references: 18342851
references: Physiol Behav. 2010 Jan 12;99(1):33-9
references: 19835896