A Pilot 24-Week 'Bulk and Cut' Dietary Protocol Combined with Resistance Training Is Feasible and Improves Body Composition and TNF-α Concentrations in Untrained Adult Males

Abstract

Background/Objectives: This study piloted a 24-week bodybuilding program combining resistance training (RT) with a dietary bulk-and-cut protocol in middle-aged adult males. Methods: Seven untrained males (33 ± 3.0 years; BMI = 35.0 ± 4.6 kg/m²; body fat = 36 ± 5%) completed a 24-week intervention combining RT with a dietary protocol consisting of 12-week cycles of caloric bulking (0-12 weeks) and cutting (12-24 weeks). The participant retention rate was 64%, while compliance with training was 96.7%, and adherence to dietary cycles was over 93%. To assess the preliminary efficacy of the intervention, venous blood samples and measurements of body composition (BodPod), muscle strength, and VO₂max (cycle ergometer) were collected at baseline (week 0) and following the bulking (week 12) and cutting (week 24) cycles. Circulating lipids (triglycerides, total, low-density, and high-density cholesterol), C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10) were measured in serum. Results: The training led to significant increases in muscle strength, especially in the deadlift (+46%, p < 0.001) and squat (+65%, p < 0.001). Improvements in body composition were characterized by an increase in fat-free mass and a decrease in body fat percentage over the 24-week intervention (+3% and -6%, respectively, p < 0.05). Lipids, CRP, IL-6, and IL-10 did not change significantly, but there was a notable reduction in TNF-α (time effect p = 0.05, _pη² = 0.39), with 15% lower concentrations at week 24 compared to baseline, indicating reduced inflammation. Conclusions: Overall, the pilot intervention achieved high compliance and adherence rates, leading to improvements in body composition and lower resting TNF-α concentrations in a group of middle-aged males with obesity.

Keywords: blood lipids; exercise and diet intervention; inflammation; obesity.

Figure 1

Study timeline (created in BioRender.com).

Figure 2

CONSORT study diagram.

Figure 3

Relative changes in triglycerides, total cholesterol, HDL cholesterol, and LDL cholesterol from baseline (week 0) to post-bulking (week 12) and post-cutting (week 24) cycles in adult males with overweight and obesity (n = 7). Data are expressed as mean ± standard deviation.

Figure 4

Relative changes in C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL6), and interleukin 10 (IL10) from baseline (week 0) to post-bulking (week 12) and post-cutting (week 24) cycles in adult males with overweight and obesity (n = 7). Data are expressed as mean ± standard deviation. * Denotes a significant difference compared to baseline and week 12 (p < 0.05).