Training while your appetite is switched off is a different problem from ordinary motivation. Here is how to think about it without either forcing it or giving it up.
Movement is worth protecting, and resistance training in particular is what researchers are betting on. The LEAN-P trial is randomising 232 adults starting semaglutide or tirzepatide to home-based resistance exercise three times a week, protein supplementation at 1.6 g per kg per day, both, or neither.2 But exercising hard while eating very little is how people end up dizzy, foggy, and worse off. The workable position is to keep training, lower the intensity on bad days, and fix intake first.
The usual advice about pushing through does not quite apply, because the thing making you tired is also the thing stopping you refuelling.
On a GLP-1, decreased appetite is an expected effect of the medication.3 Normally a hard session makes you hungry and you eat more. Here the hunger signal is suppressed, so the extra demand does not get met. Train hard enough for long enough in that state and you are simply running a larger deficit, which shows up as exactly the flat, foggy tiredness described in GLP-1 tired all the time.
That is the real reason people feel like exercise is not working for them on these medications. It is usually a fuelling problem wearing a motivation costume.
The LEAN-P trial is a six-month randomised controlled trial enrolling 232 adults with obesity who are starting semaglutide or tirzepatide. Participants are randomised to one of four arms: control, resistance exercise, protein supplementation, or both combined. The exercise intervention is home-based, three sessions a week, progressing from one to three sets targeting major muscle groups, and the protein arm targets 1.6 g per kg of body weight per day.2
Two things to take from that. First, the structure is deliberately modest and home-based rather than heroic, which is a reasonable template while your appetite is suppressed. Second, it is a protocol, so the results are not in. The design tells you what experienced researchers consider a sensible bet, not what has been proven to work.
The reason they are testing it is a concern about lean mass during rapid weight loss. That concern is real enough to fund trials against, but it is not settled, and systematic reviews of imaging data have been more reassuring than the headlines. Brain fog, meanwhile, remains a symptom with several drivers rather than a diagnosis, so tiredness around training is worth tracing to intake before blaming the training.1
Exercise intolerance that is getting worse rather than better, faintness, or a heart rate that feels wrong for the effort are all reasons to stop and speak to the clinician who manages your care, especially if you also take insulin or a sulfonylurea. The same goes for severe or persistent vomiting or diarrhea and signs of dehydration.3 Do not change or stop your medication on your own.
Pre-workout products are usually heavily caffeinated, which tends to sit badly on a nauseated stomach, so some people look at non-stimulant options instead. Lion's Mane (Hericium erinaceus) is a culinary mushroom examined in a small double-blind pilot trial that measured cognitive performance, stress, and mood in young adults.4 That is early evidence from a small field, it is not a performance supplement, and it was not studied alongside these medications. Clear additions with your clinician.
Keep moving, but lower the intensity rather than forcing your normal session. The tiredness is usually a fuelling problem, and training hard while eating very little tends to make the fog and fatigue worse rather than better.
Resistance training is what researchers are specifically testing. The LEAN-P trial uses home-based resistance sessions three times a week, progressing from one to three sets targeting major muscle groups, alongside a protein target.
Generally yes, and on a schedule rather than waiting for hunger, since hunger is the signal the medication suppresses. Something small and protein-led is better than training completely unfed. Your clinician or a dietitian can help set this properly.
It can reflect low intake, dehydration, or low blood sugar, which is more likely if you also take insulin or a sulfonylurea. Listed low blood sugar symptoms include dizziness, shakiness, sweating, and weakness. Stop and speak to your clinician rather than pushing on.
That is being tested rather than settled. Resistance training and adequate protein are the interventions under study for preserving lean mass during GLP-1 therapy, and they are sensible habits regardless, but the trial results are not yet available.
Consult your prescriber. Do not start, stop, or change any prescription medication or add a new supplement without talking to the clinician who manages your care. This page is educational and is not medical advice, diagnosis, or treatment.
FDA disclaimer. Statements about dietary supplements have not been evaluated by the FDA. Supplements are not intended to diagnose, treat, cure, or prevent any disease.