Figure 2.

Positive and negative lifestyle factors influence obesity and the immune system. The negative lifestyle factors (red) can lead to a disbalance in immune homeostasis, trained innate immunity, inflammaging, and a decrease in infection resistance. Positive factors (green) can protect immune homeostasis and potentially increase resistance to infection. Trained innate immunity: long term functional reprogramming of innate immune cells, which is evoked by exogenous or endogenous stimuli and which leads to a usually enhanced response toward a second challenge after return to a non-activated state. Inflammaging: chronic low-grade inflammation that occurs with aging and is characterized by dysregulated inflammatory responses, in general resulting in increased inflammatory responses and diminished responses to pathogens like influenza or SARS-CoV-2.