Maintaining an adequate prepper food supply is vital to survival during any long-term disaster situation. While technically you could stay alive without food for around 30 days, you may wish you hadn't. Hunger can itself lead to dehydration. Over time the body breaks down fat and muscle tissue in order to keep itself powered causing pain when moving. Eventually, extreme hunger leads to low energy, apathy about the situation and eventually death. Because hunger is an insidious killer, it is imperative to stock enough emergency food supplies to maintain your health and energy.
Many doomsday preppers will stock-up on canned food, or MREs (Meals Ready to Eat). But I wouldn't count on being able to use much of that food. Consider that you may actually have to bug-out on foot, and leave most of that heavy canned food at home. Remember that cars may not work if there has been a bad solar storm, or the roads may be blocked if everyone in your area is trying to evacuate all at once. And both canned food, and MREs very heavy due to their high water content, making it difficult to carry. I’m not against stocking-up on canned food – I’m against people counting on being able to actually use that canned food.
So a well thought out bug-out bag should allow for these contingencies. In prepping for doomsday you'll want to maintain your bug-out bag with as much light-weight, nutrient-dense prepper food as you can carry. Rest assured there is no reason you can't pack enough food in your bug out bag for at least 3 months. Many of the popular Grab-and-Go Food buckets claim to support one adult for 2 months and only weight 10 lbs. To supplement this survival food bars can provide extra calories when needed.