Purpose: The carbohydrate-restricted diet has been recognized to be effective into preventing and alleviating lifestyle-related diseases, such as obesity and type 2 diabetes. The rare sugar D-allulose is a functional monosaccharide with anti-obesity effects. In the present study, we examined the effects of dietary D-allulose on body fat accumulation in rats fed severely carbohydrate-restricted diets containing high concentrations of different fats, beef tallow, or soybean oil. Methods: Male Wistar rats (n = 35, 3-week-old) were divided into 5 groups: One chow-fed control (C) group, and four carbohydrate-restricted groups, namely, beef tallow (B), beef tallow + D-allulose (BA), soybean oil (S), and soybean oil + D-allulose (SA), with free access to the diet and water for 8 weeks. The B and BA diets contained 23% beef tallow and 2% soybean oil, whereas the S and SA diets contained 25% soybean oil. Furthermore, the BA and SA diets contained 5% D-allulose. Results: The final body weight, weight gain, and food intake were significantly higher, and food efficiency was significantly lower in the control group compared to the other carbohydrate-restricted groups. Intra-abdominal adipose tissue, carcass fat, and total body fat weights were not influenced by dietary fat type or D-allulose supplementation, except for the epididymal adipose tissue weight. In contrast, carbohydrate restriction suppressed body weight gain in rats, but remarkably increased body fat accumulation. Conclusion Under carbohydrate-restricted conditions, no anti-obesity effects of dietary D-allulose were observed, regardless of the dietary fat type. The causes of these effects are unknown. However, they may be influenced by a very low carbohydrate and high protein diet. Further research is required to elucidate the effects of D-allulose under various nutrient compositions with different fat, carbohydrate, and protein energy ratios.