Low Power and Lossy Networks (LLNs) have a crucial role in the Internet of Things (IoT) paradigm. For the IPv6 Routing Protocol for LLNs (RPL), two objective functions (OF) have been standardized so far, namely (Objective Function zero (OF0), and the Minimum Rank with Hysteresis Objective Function (MRHOF). However, these particular objective functions are used to build a topology where bottleneck nodes may suffer from an excessive unbalanced traffic load. As a result, a part of the network may be disconnected as the energy of the overburdened preferred parent node will drain much faster than other candidate parent nodes. Thus, in this paper, we propose a new objective function that balances the number of children nodes for the overburdened nodes to ensure node lifetime maximization. To implement this OF, we amended the DIO message format. By using a new utilization technique, we also mitigated any potential extra overhead. Finally, a new RPL metric has been introduced to balance the traffic load over the network. Simulation experiments have been conducted to examine the performance of our new approach. Collected results corroborate the superiority of our objective function over the existing ones in terms of lifetime, power consumption and packet delivery ratio.