It's usually not an allergy
The most common thing I see when someone tells me they bloat on training days is a reasonable diet, eaten at an unreasonable hour relative to the session. Before anyone eliminates a food group, it's worth ruling out the boring explanations, because they account for most cases and they're much cheaper to fix.
Blood flow gets redirected away from digestion during hard effort. If there's still a substantial meal being processed when that happens, it sits. That's not intolerance, that's scheduling.
The three usual suspects
1. Timing
A large mixed meal generally needs two to three hours before hard training. Something smaller and carb-led needs closer to one. If you're eating ninety minutes out and feeling heavy, try moving the meal rather than removing anything from it.
2. Fat content
Fat slows gastric emptying. It's genuinely useful most of the time and unhelpful in the two hours before a session. This is why the same meal can be fine at lunch and miserable pre-training, it isn't the food, it's the clock.
3. Fermentable fiber
Beans, certain fruits, and some vegetables ferment in the large intestine and produce gas. That process is a sign of a working microbiome, not a problem, but it's badly timed if it peaks mid-session. Keep them, move them earlier in the day.
How to actually find your answer
Change one variable at a time and give it a week. This is where photographing meals earns its keep: after ten days there's a pattern visible in the timeline that nobody can reconstruct from memory. In coaching I'm looking at the gap between the meal and the session, the fat content, and the fiber load, in that order.
When it isn't any of those
If you've worked through timing, fat and fiber and the bloating is persistent, especially with pain, blood, unintended weight loss, or a change that came on suddenly, that's a conversation with your doctor, not your coach. Coaching works alongside medical care. Knowing where the line is is part of the job.
Working on this yourself? This is ground PATH Fuel covers over its twelve weeks. If you'd like someone looking at your actual week rather than general advice, that's what the coaching is.
This article is general education for healthy adults. It isn't medical advice and it isn't a substitute for your own doctor or provider. If something's persistent, painful, or new and unexplained, get it looked at.