Owing to agricultural expansion worldwide, agricultural crops can have major effects on the life history traits of wildlife. However, the functional role of crop consumption on the life history traits of long-lived mammals is seldom evaluated quantitatively. Body size is an important life history trait because it is directly related to fitness. In this study, we investigated the functional role of long-term crop consumption on body growth of sika deer (Cervus nippon). Crop consumption accelerated body growth of not only the consumer but also the next generation, and its effect differed by sex. In females and males, the degree of crop consumption produced maximum differences of about 2 and 1 years in the ages at which 98% asymptotic size was attained, respectively. However, this difference did not always occur in males. The degree of crop consumption by mothers generated a maximum difference of about 15% in the hind-foot length of their fetus. This study revealed that the degree of long-term crop consumption affects the body growth of deer at an individual level, even within the same population. The crop consumption had a positive effect on the consumer and the next generation. Further examination of the effects of accelerated body growth on population growth rates will elucidate more accurately the effects of crop consumption on population dynamics in the landscape, including agricultural crop lands.