A cafeteria diet modifies the response to chronic variable stress in rats

Figures & data

Table I.  Nutrient composition of the HC and HF diets and of cafeteria diet food items.

	Monotonous diets		Cafeteria diet food items
	HC^*	HF^†	Standard high carbohydrate^‡	“Kit Kat” chocolate^¶,§	“Digestive” biscuits^‖,§	Peanut butter^#,§
Protein (% wt)	19	16.5	19	7.6	6.3	23.6
Carbohydrates (% wt)	65.3	53	65.3	59.1	67.7	12.5
Sugars	9.2	7.5	9.2	43.7	13.6	6.3
Fat (% wt)	9.6	25	9.6	26.2	21.8	46.8
Fat breakdown
Saturated fat (%)	18	34^**	18	13	48	68
Monounsaturated fat (%)	29	38^**	29	46	0	0
Polyunsaturated fat (%)	47	34^**	47	41	52	32
Fiber (% wt)	4.3	3.6	4.3	3	3.5	6.2
Metabolizable energy (kJ/g)	17.7	21	17.7	21.1	20.7	24.5
Energy (protein %)	18	13	18	47	22	26
Energy (carbohydrate %)	62	42	62	13	68	59
Energy (fat %)	20	45	20	24	6	8

Notes: Food composition data are provided by the manufacturers' information or food tables. Data are not corrected for evaporation

^* Laboratory rodent starter diet no. 1, Hawa Chicken Co. (Safra, Lebanon)

^† Diet derived from the standard HC diet enriched with added oils (same procedure as Daher et al. 2006)

^‡ Hawa chicken rodent starter diet no 1, Lebanon

^¶ Nestle S.A. (Switzerland)

^§ Items shown to cause hyperphagia in rats fed cafeteria-type diets (Shafat et al. 2009)

^‖ McVitie's, United Biscuits (Hayes, Middlesex, UK)

^# Monarch (San Ramon, California, USA)

^** Values were chosen to match the average fatty acid composition of the cafeteria diet consumption for six rats during 5 days (separate preliminary study).

Table II.  Schedule of stressor agents used during the chronic stress treatment.

Day of treatment	Stressor used	Duration	Time of administration
1	Flashing light	4 h	12:00–16:00
2	Neighbor cage	14 h	17:00–07:00
3	Cage tilt	3 h	10:00–13:00
4	Space reduction	4 h	08:00–12:00
5	No stressor	x
6	Flashing light	4 h	14:00–18:00
7	Forced swimming (warm)	10 min	12:00–12:10
8	Restraint	1 h	09:00–10:00
9	Cage tilt	4 h	08:00–12:00
10	Flashing light	3 h	12:00–15:00
11	Neighbor cage	14 h	17:30–07:30
12	No stressor	x
13	Cage tilt	3 h	11:00–14:00
14	Restraint	3 h	10:00–13:00
15	Flashing light	4 h	14:00–18:00
16	Forced swimming (cold)	10 min	15:00–15:10
17	Restraint	2 h	12:00–14:00
18	Space reduction	5 h	08:00–13:00
19	No stressor	x
20	Restraint	2 h	09:00–11:00
21	Forced swimming (warm)	10 min	16:00–16:10

Figure 1.  Energy intake (kJ/rat/day) of rats fed a high-carbohydrate, high-fat, or cafeteria diet and either submitted to a CVS paradigm or not during weeks 3–6. Data are expressed as the mean ± SEM. *Statistical difference with regard to the first 3 weeks. ^aStatistical difference with regard to the high-carbohydrate dietary group in the same stress condition. p < 0.05 is considered significant. Note: there was no significant difference between the energy intake of stressed and non-stressed animals.

Table III.  Energy intake (kJ/rat/day) from different cafeteria items of rats fed a cafeteria diet and either submitted to a CVS paradigm or not during weeks 4–6.

		Weeks 4–6
	Weeks 1–3	Non-stressed rats	Stressed rats
Peanut butter	30.1 ± 1.2^d	28.4 ± 1.5^c	21.4 ± 1.8^* ^,d
Chocolate	37.4 ± 2.1^c	34.9 ± 2.4^c	29.6 ± 1.7^* ^,c
Biscuits	87.4 ± 3^a	91.2 ± 2.1^a	84.3 ± 4.1^a
Standard HC	72.6 ± 2.9^b	75.9 ± 1.9^b	66.3 ± 2.2^* ^,b

Notes: Data are expressed as the mean ± SEM. Means within each column with different letters (a–d) differ significantly (p < 0.05)

* Statistical difference with regard to the first 3 weeks.

Figure 2.  Percentage of sucrose solution from the total liquid ingested during 2 h in rats fed a high-carbohydrate, high-fat, or cafeteria diet and either submitted to a CVS paradigm or not (n = 8). Data represent the average of three sucrose preference tests conducted during weeks 4–6 of the experiment. Results are expressed as mean ± SEM. *Statistical difference with regard to the non-stressed group having the same diet. p < 0.05 is considered significant.

Table IV.  Body weights, body weight gain, and abdominal fat for rats fed a standard chow, high-fat, or cafeteria diet and either submitted to a CVS paradigm or not (n = 8).

	High-carbohydrate diet		High-fat diet		Cafeteria diet		Statistical significance
	Non-stressed	Stressed	Non-stressed	Stressed	Non-stressed	Stressed	Effect of diet	Effect of stress	Interaction of diet with stress
Final body weight (g)	378 ± 4.1	374.5 ± 5	382.5 ± 11.1	371.5 ± 3.1	407.5 ± 12^*,†	395.6 ± 9.4^*,†	0.029	n.s.s.	n.s.s.
Total body weight gain (g)	130 ± 1.9	125.1 ± 2.1	124.9 ± 3.1	120.8 ± 2.9	158.5 ± 4.1^*,†	149.6 ± 3.7^*,†	0.017	n.s.s.	n.s.s.
Total weight gain in weeks 1–3 (g/day)	3.7 ± 0.1	3.9 ± 0.1	3.3 ± 0.2	3.3 ± 0.3	4.2 ± 0.2^*,†	4.4 ± 0.3^*,†	0.03	n.s.s.	n.s.s.
Total weight gain in weeks 4–6 (g/day)	3 ± 0.1	1.9 ± 0.2	3.5 ± 0.2	2.5 ± 0.2	4.1 ± 0.2^*,†	2.6 ± 0.3^*	0.04	0.024	n.s.s.
Abdominal fat percent (% body weight)	1.23 ± 0.01	1.33 ± 0.2	1.6 ± 0.1	1.6 ± 0.1	2.8 ± 0.4^*,†	2.5 ± 0.5^*,†	p < 0.001	n.s.s.	n.s.s.

Notes: Data are expressed as the mean ± SEM. p < 0.05 was considered significant. n.s.s., non-statistically significant (p>0.05)

* Statistical difference with regard to the standard chow dietary group in the same stress condition

^† Statistical difference with regard to the high-fat dietary group in the same stress condition.

Table V.  Serum lipid parameters for rats fed a standard chow, high-fat, or cafeteria diet and either submitted to a CVS paradigm or not (n = 8).

	High-carbohydrate diet		High-fat diet		Cafeteria diet		Statistical significance
	Non-stressed	Stressed	Non-stressed	Stressed	Non-stressed	Stressed	Effect of diet	Effect of stress	Interaction of diet with stress
Total cholesterol (mg/dl)	76.4 ± 11.2	90.6 ± 10.5	95.4 ± 10.5	124.3 ± 10.58^*,†	92.2 ± 10.5	122.9 ± 13.3^*,†	p = 0.05	p = 0.009	n.s.s.
Triglycerides (mg/dl)	136.3 ± 16.5	123.9 ± 18.2	108 ± 15.4	136.1 ± 14.4	107.5 ± 15.4	155.5 ± 15.4	n.s.s.	n.s.s.	n.s.s.
HDL (mg/dl)	50 ± 3.1	46.4 ± 2.8	50.6 ± 4.5	41.5 ± 2.1	41.2 ± 3.1^†	37.9 ± 2.2^†	p = 0.034	n.s.s.	n.s.s.
LDL (mg/dl)	33.5 ± 7.5	44.2 ± 6.1	50.2 ± 14.2	87.9 ± 11.4^*,†	51 ± 10.2	84.9 ± 10.1^*,†	p = 0.023	p = 0.005	n.s.s.

Notes: Data are expressed as the mean ± SEM. p < 0.05 was considered significant. Values from the table may differ from text values because they refer to individual group values rather than clustered values for an effect. n.s.s., non-statistically significant (p>0.05)

* Statistical difference with regard to the non-stressed group having the same diet

^† Statistical difference with regard to the high-carbohydrate dietary group in the same stress condition.

Figure 3.  Serum corticosterone concentration (ng/ml) of rats fed a standard chow, high-fat, or cafeteria diet and either submitted to a CVS paradigm or not (n = 8). Data are expressed as the mean ± SEM. *Statistical difference with regard to the non-stressed group having the same diet. p < 0.05 is considered significant.

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