Background: Childhood obesity is a global health concern. Conventional nutrition guidelines have come under scrutiny in helping to achieve long-term healthy weight. An alternative carbohydrate-restricted, higher fat approach has shown to be effective in adults, but research is limited in youth. Aim: To assess the feasibility of a 12-week whole-food, carbohydrate-restricted diet on weight loss and metabolic health. Setting: Overweight children aged 8–13 years. Methods: In this single-arm study, 25 overweight children were provided with whole-food, carbohydrate-restricted dietary guidelines. Primary outcomes – dietary acceptability, adherence and affordability – were assessed qualitatively weekly (telephone) and post-intervention (focus groups). Secondary outcomes – Body mass index (BMI), waist circumference, lipids and glycaemic control measures – were assessed at 0 and 12 weeks. Change scores were analysed using the t-statistic and interpreted using the statistical significance threshold, p < 0.05. Results: Overall, dietary acceptability was mostly positive, and reports of affordability by parents were mixed. Attrition rates were high (48%); adherence was influenced, positively and negatively, by levels of support from friends and family. Completing children reduced BMI by 2.1 ± 1.5 kg.m2 (p < 0.05). Key blood parameter changes included a reduction in triglycerides (−0.17 ± 0.48 mmol/L; p = 0.242) and an increase in high-density lipoprotein (HDL) cholesterol (0.24 ± 0.19 mmol/L; p < 0.05). Conclusion: Children achieved some weight loss and health outcome success using this dietary approach. For sustainable weight loss maintenance, full family and health professional support, particularly on a more intensive level at the start, may be required.