The effects of a short term (14 day) dietary substitution on body composition and biomarkers of metabolic health in healthy adults

The Special K Challenge is a partial meal replacement plan whereby two main meals are substituted with a fixed portion of Kellogg‟s Special K and semi-skimmed milk for two weeks. It is designed to reduce energy intake sufficient to reduce body mass and waist circumference in order to encourage long term body mass reduction. The present study aimed to evaluate the effects of the Special K Challenge on body composition and biomarkers of fat metabolism in healthy adults. Twenty four subjects (12 men and 12 women) with a mean age of 34.7 (11.7) and mean body mass index of 28.6 (2.9)kg/m2 were recruited via email from the University of Limerick campus. Dietary intake and body composition was measured over a two week period to establish a basal level (BASAL) prior to the two week Special K Challenge (DIET). Dietary intake was assessed by interview and dietary recall using food diaries. Body composition was measured using bioelectrical impedance (BIA) and dual energy X-ray absorptiometry (DXA). Blood serum and plasma were analysed for total, LDL and HDL cholesterol, triglycerides, glucose, insulin, leptin and adiponectin. The Special K Challenge induced a mean energy deficit of 673 (360)kcal (p < 0.001). The macronutrient contribution to total energy intake was favourably improved closer to the recommended daily intake. Total body mass was reduced by a mean of 1.7 (1.4)kg (p < 0.001). Fat and fat free mass were reduced by 0.7 (0.8)kg (p < 0.001) and 0.9 (1.0)kg (p < 0.05) respectively. Abdominal fat mass as represented by the L1-L4 region of interest and waist circumference was reduced by 0.17(0.15)kg and -1.9(1.7)cm respectively (p < 0.001). No statistically significant effect on total, LDL or HDL cholesterol, triglycerides, glucose or insulin was observed. The results of the present study demonstrate that the Special K Challenge was effective in reducing total energy intake and resulted in a positive, health-related change in body composition. The reduction in total body mass, regional fat mass and waist circumference may act as an effective motivator to long term body mass reduction.