<p><strong>Background</strong>: Many individuals continue to smoke despite the known harmful effects of cigarette smoking. Tobacco harm reduction (THR) is a public health strategy that seeks to reduce or prevent projected harm caused by cigarette smoke via encouraging smokers, who would otherwise continue to smoke, to switch to products with reduced risk profiles (such as e‑cigarettes). Research shows smoking can influence numerous physiological and psychological functions such as appetite,

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... itive function and emotion. For some smokers, the loss of such effects upon cessation has been cited as an incentive to resume smoking. The effect of e‑cigarettes (and other non-combustible alternatives to cigarette smoking) on the above-described physiological and psychological functions has not been widely researched. Such information may be important for more thoroughly evaluating the proposition that smokers seeking alternatives may find e-cigarettes a satisfactory substitute for conventional cigarettes.</p><p><strong>Methods</strong>: This randomised, partially blinded, crossover study will test the hypothesis that use of a nicotine containing e-cigarette can influence appetite to the same extent as a combustible cigarette following a period of nicotine abstinence in current smokers. Up to 40 current smokers will be recruited into the study. Enrolment started in February 2021 and the results from the study are expected in 2022.</p><p><strong>Conclusions</strong>: The data from this study will be a valuable addition to the growing body of literature about the potential of e-cigarettes as a satisfactory and viable long-term alternative to cigarettes for existing smokers.</p><p class="abstract"><strong>Trial Registration: </strong>This study is registered with the ISRCTN registry, number ISRCTN72435551.</p>