Sugar negatively impacts energy levels and mood by causing rapid spikes and subsequent crashes in blood sugar. This fluctuation can lead to feelings of fatigue, irritability, and anxiety. Consuming high-added sugar foods can result in short-term energy boosts, followed by energy slumps that affect overall mood stability. Over time, excessive sugar intake may contribute to insulin resistance and increase the risk of related health issues, emphasizing the importance of moderating sugar consumption for better mental and physical health.