Low blood sugar can put people into a bad mood and make them aggressive. But let me argue that the implications of this fact are a little different than some might naively think.

A big cause of low blood sugar is when you have eaten sugar, refined carbs or some other food with a high insulin index a couple of hours earlier. When sugar, refined carbs or something else high on the insulin index causes insulin to spike, that insulin causes blood sugar to be removed from the bloodstream (some to the muscles and some to be stored as fat in the fat cells). It is like waking up from being asleep at the wheel, seeing you are drifting off to the right, and then overcorrecting to the left. 

So, a good way to reduce the chances of blood sugar low enough to make you "hangry" is to avoid sugar, refined carbs and other foods high on the insulin index. If you do avoid sugar, refined carbs and other foods high on the insulin index, you will find that you don't need food handy in order to avoid being hangry. Indeed, if, when you do eat, you eat foods low on the insulin index, you can skip meals entirely and still have a reasonable level of blood sugar because keeping insulin low leads your body to make blood sugar from the fat in your fat cells.  

Many, many people in the US think of skipping a few meals as if it were torture. And that is the way skipping meals will seem to you if when you do eat, you eat sugar, refined carbs and other foods high on the insulin index.

People often blame bad nutrition on eating "processed foods." There is a lot of truth to this, if only because most processed foods contain a lot of sugar or some kind of flour or starch that your body quickly converts into sugar. It is easy to verify the high sugar content of most processed foods by looking at the ingredients on the side of the package if you know all the different names for various kinds of sugar. Googling "top types of sugar in processed foods" I came immediately to an post by "Dr. Axe" with this useful list of different types of sugar you might find on an ingredient list:

• Corn syrup or high-fructose corn syrup
• Dextrose or crystal dextrose
• Fructose
• Maltose
• Lactose
• Sucrose
• Glucose
• Evaporated cane juice or fruit juice
• Caramel
• Carob syrup
• Brown sugar
• Raw sugar
• Dextrin and maltodextrin
• Rice syrup
• Molasses
• Evaporated corn sweetener
• Confectioner’s powdered sugar
• Agave nectar
• Other fruit nectars (for example, pear nectar)

For most processed foods, the sugar content is high enough to cause enough harm that it is not so easy to tell whether there is also something else in a particular processed food that also causes substantial harm.

Of course, it isn't sugar per se, but anything that spikes insulin that is the problem. To learn more about which foods are high on the insulin index, see "Forget Calorie Counting; It's the Insulin Index, Stupid." To learn more about the insulin theory of obesity, see my post "Obesity Is Always and Everywhere an Insulin Phenomenon." 

You might also be interested in these other related posts:

• The Keto Food Pyramid
• Mass In/Mass Out: A Satire of Calories In/Calories Out
• Jason Fung: Dietary Fat is Innocent of the Charges Leveled Against It
• Faye Flam: The Taboo on Dietary Fat is Grounded More in Puritanism than Science
• Sugar as a Slow Poison
• Katherine Ellen Foley—Candy Bar Lows: Scientists Just Found Another Worrying Link Between Sugar and Depression
• Ken Rogoff Against Sugar and Processed Food
• Kearns, Schmidt and Glantz—Sugar Industry and Coronary Heart Disease Research: A Historical Analysis of Internal Industry Documents
• Salt Is Not the Nutritional Evil It Is Made Out to Be
• Whole Milk Is Healthy; Skim Milk Less So
• How the Calories In/Calories Out Theory Obscures the Endogeneity of Calories In and Out to Subjective Hunger and Energy
• Putting the Perspective from Jason Fung's "The Obesity Code" into Practice
• Julia Belluz and Javier Zarracina: Why You'll Be Disappointed If You Are Exercising to Lose Weight, Explained with 60+ Studies (my retitling of the article this links to)
• Meat Is Amazingly Nutritious—But Is It Amazingly Nutritious for Cancer Cells, Too?
• Diana Kimball: Listening Creates Possibilities
• On Fighting Obesity
• Analogies Between Economic Models and the Biology of Obesity
• Debating 'Forget Calorie Counting; It's the Insulin Index, Stupid'

Also see the last section of "Five Books That Have Changed My Life."