Probably not nuts for deliberate snacking amidst exercising. Also (nice as they are) too many Brazil nuts are not good for most people, since they can bring about selenium toxicity. Getting the dietary balance right is confusing and complicated, even without allowing for each of us being different and responding differently to any one treatment or food type.
It's worth trying to pin down exactly what works best for you,
@Taffyboyslim. In an ideal (often impractical) world you'd pause during the steep hike when you felt weak, finger prick to establish your BG at that moment then try an energy bar, or cereal /protein bar, or toffees / boiled sweets and see which helped most. Different trials - not all at once. Hopefully that would lead YOU towards practical snacks that were easy to carry, open and get stuck into for quick recovery - in sun, drizzle or torrential rain.
The plain old Snickers / Mars bars are likely to fall into the "probably not" category since the fat in the chocolate can be slow to digest for many people and if you're feeling noticeably weak ("running out of gas" as
@davidj said) then you are after a quick response. But you might be fine with one of those. For me things like boiled sweets or Wurther's toffees provide that speedy response: sucking them is faster digested and into your blood, than chewing/crunching and swallowing and waiting for stomach digestive juices do their stuff. I love a bag of crisps, but the contents are easily turned into crumbs and become packet opening hassle, soggy in any rain - so crisps (for me) need a deliberate, sheltered, hiking pause. As does a sandwich. Bananas can work, if reasonably well protected in my backpack; but pausing, getting the banana out and unpeeling it isn't always a slick process.
The other thing is how steep is the hike? I.e. has a long walk become intense anaerobic exercise rather than extended, regular aerobic exercise? I suspect anaerobic conditions are managed more urgently by our brains. Our body's response mechanisms are triggered by an array of different hormones and for people with normal pancreatic functions our brain uses the glucagon hormone in the pancreas to trigger the liver to release extra glucose when needed. [Brain can't talk directly to the liver. Who knew its not that clever?] I'm T3c, have absolutely no pancreas so no source of glucagon hormone (as is
@sololite). But if I've run out of gas, my brain might look for a different mechanism; perhaps make me anxious and trigger adrenaline or stressed and trigger cortisol - finding a way of getting some sort of glucose release from the liver and thus recovery. If the liver has anything left in the store. In extremis, my brain might make me collapse, fall down and get my head lower than my heart - just to maintain blood flow to my brain.
Before this extreme scenario the boiled sweets are simpler (but not if they're in that impossible to open tin) and keep me ahead of possible events, even if the wrappers are inadequate and the sweets have too much fluff around them! The hard boiled egg still in its shell is less convenient. Trial and learning is a big feature of managing our D and our physical limitations even for people without D.