Clenbuterol can induce fat burning via beta-2-adrenergic agonism; it is a highly selective B2 agonist. Via this mechanism, it induces fat burning by increases intra-cellular levels of cyclic AMP which has downstream effects on inducing protein kinase A (PKA) activity  which then acts on hormone sensitive lipase (HSL) and perilipin to mediate lipolysis;  insulin is a negative mediator of this pathway.  PKA may also induce CREB phosphorylation, which is then able to induce JHDM2a (a histone demethylase) promoter activity  and may have downstream influences on PPARα and UCP1, two proteins involved in fatty acid oxidation and uncoupling (respectively).
While the use of inhaled LABAs are still recommended in asthma guidelines for the resulting improved symptom control,  further concerns have been raised, by a large meta-analysis of the pooled results from 19 trials with 33,826 participants, that salmeterol may increase the small risks of asthma deaths, and this additional risk is not reduced with the additional use of inhaled steroids (., as with the combination product fluticasone/salmeterol ).  This seems to occur because although LABAs relieve asthma symptoms, they also promote bronchial inflammation and sensitivity without warning.