Eat an Egg.
Eggs are great for helping you feel fuller for longer. Mainly due to the fat and protein content, eggs provide a longer and slower energy release. Recent research has proven that an egg at lunchtime is perfect for avoiding that afternoon tiredness. Egg whites contain the right combination of proteins that the body needs, especially with regards to that mid-afternoon dip that so many people experience.
That mid-afternoon fatigue is also in part due to our own body's internal rhythms, someone known as a BRAC-cycle (Basic Rest-Activity Cycle) where we up our ups and downs in terms of energy patterns throughout the day. So, as well as having energy cycles, we also have nutritional cycles (appetite) and it is important to be able to match these. For example, a light, carbohydrate-rich breakfast won't be sufficient for the morning activity cycle, which is why some people are prone to what appears to be "hypoglycaemia" when they have no medical underlying cause such as diabetes. There is a mismatch between the fuel they provide their body and the body's needs.
Adding an egg to breakfast can help change this, as it provides some of the additional protein that the body requires, along with some fats, for slow energy release helping to avoid that apparent hypoglycaemia.
How you cook the egg is important. A raw egg drunk down with a mix of milk and spices used to be quite popular but isn't for everyone, and of course, there is that salmonella risk. Frying in light oil (not lard!) is ok, but you may want to keep the extra fats down, so stick with boiled or poached.