Caloric Restriction and Formalin-Induced Inflammation: An Experimental Study in Rat Model

Acute and chronic inflammations are difcult to control. Using chemical anti-inflammatory medications along with their
complications considerably limit their use. According to Traditional Iranian Medicine (TIM), there is an important relation between
inflammation and Imtila (food and blood accumulation in the body); food reduction or its more modern equivalent Caloric Restriction
(CR) may act against both Imtila and inflammation.
Objectives: This experimental study aimed to investigate the effect of 30% reduction in daily calorie intake on inflammation in rats.
Materials and Methods: A total of 18 male rats (Rattus rattus) weighing 220 to 270 g were obtained. Then, the inflammation was induced
by injecting formalin in their paws. Next, the rats were randomized by generating random numbers into two equal groups (9 + 9) putting
on either normal diet (controls) or a similar diet with 30% reduction of calorie (cases). Paw volume changes were recorded twice per day
by one observer in both groups using a standard plethysmometer for 8 consecutive days. Serum C-reactive protein (CRP), Erythrocyte
Sedimentation Rate (ESR), complete blood count (erythrocyte, platelet, and white blood cell) and hemoglobin were compared between
the groups.
Results: Decline of both body weight and paw volume was signifcantly more prominent in the case than in the control rats within the
study period (P < 0.001 and < 0.001, respectively). Paw volume decrease was more prominent after day 3. On day 8, serum CRP-positive (1
or 2 +) rats were more frequent in ad libitum fed group comparing with those received CR (33.3% vs. 11.1%). This difference, however, was
insignifcant (P = 0.58). At the same time, mean ESR was signifcantly higher in the control rats comparing with that in the case group
(29.00 ± 2.89 h vs. 14.00 ± 1.55 h; P = 0.001). Other serum parameters were not signifcantly different between the two groups at endpoint.
Conclusions: Rats fed with a 30% calorie-restricted diet in comparison with to ad libitum fed controls for 8 days had signifcantly more
prominent regression of inflammation.