With regard to the beneficial impact of lifestyle interventions on weight and abdominal obesity management, our objective was to identify which components of a lifestyle-intervention program [physical activity (PA), energy and macronutrient intake, diet quality] had an influence on visceral adipose tissue (VAT) loss. The present lifestyle intervention targeted a daily energy deficit (500 kcal), coupled with a PA program (160 min/wk). From the 144 participants initially recruited, 93 viscerally obese men (age: 49 ± 1 y; waist circumference: 108 ± 9 cm; plasma triglyceride concentration: 2.46 ± 0.09 mmol/L) who completed a 3-d dietary journal both at baseline and after 1 y of intervention and a daily PA journal for 1 y were considered in the present analyses. Body composition and fat distribution were assessed by using dual-energy X-ray absorptiometry and computed tomography. After 1 y, abdominally obese men significantly improved their diet quality, as assessed by the Dietary Approaches to Stop Hypertension (DASH)-derived diet quality (DQ) score (P < 0.0001). Improved DQ and higher levels of PA were both independently and significantly associated with reductions in body weight, fat mass, VAT, and thigh muscle fat content, beyond reported energy intake or diet macronutrient composition. When stratified according to the level of PA and DQ [PA- (low PA), DQ- (low DQ), PA+ (high PA), DQ+ (high DQ)], the PA+/DQ+ group showed reductions in VAT that were 20% greater than in the PA-/DQ+ group, 28% greater than in the PA+/DQ- group, and 50% (P < 0.05) greater than in the PA-/DQ- group. Our results highlight the strong contribution of DQ beyond macronutrient and energy content to changes in body composition and suggest that synergistic changes in both DQ and PA levels optimally reduce VAT in men with features of metabolic syndrome. J. Nutr. 143: 1074-1083, 2013.