Two meals, two blood sugar curves, two very different energy experiences in the hours that follow.
A lunch heavy in fast carbs (white rice, white pasta, potatoes) eaten around noon sends blood sugar up fast and high. The body responds by releasing a lot of insulin to bring it back down, which drives a dip below the starting level two to three hours later, so typically between 3 and 4pm: that is the mid-afternoon energy hole. A meal with protein, fiber and good fats raises blood sugar more gently, and it comes back down without a dip.
What nutritionists and dietitians call the blood sugar crash is not in your head: it is a hormonal response, measured and documented since the 2000s. It is not a matter of willpower if hunger comes back hard two hours after a very sugary meal.
ℹ️ A recent caveat: a 2025 study (Cell Metabolism) does confirm this blood sugar and insulin pattern, but shows that felt hunger does not always follow it automatically from one person to the next. The hormonal mechanism is solid; its direct link to eating more at the next meal is less so than was thought.
Insulin has one job: to move glucose into cells. When it stays high for a long time, it also encourages the excess to be stored as fat, and it slows the use of already-stored fat as fuel. Two meals, two very different responses:
Understanding this mechanism is not a reason to cut carbs out. It is a reason to favour the ones that come with fiber, protein and good fats over fast ones eaten alone: a piece of fruit rather than juice, whole wheat bread rather than a white baguette.
Storage happens mainly in the two to three hours after a meal, for as long as insulin stays high. Burning stored fat can only happen once insulin comes back down, between meals and above all overnight: the night-time fast is the longest window without intake in the day, and therefore the body's main chance to draw on its reserves.
Snacking between meals keeps insulin continuously high and closes that window. Spacing meals out and avoiding sugary snacks after dinner, on the other hand, gives the body time to burn stored fat overnight.
In Scenario B, with a meal combining protein, vegetables and good fats, the curve stays moderate and does not cross the storage threshold, even after eating. Insulin rises gently and falls quickly, which gives the body more chances to draw on its fat between meals rather than add to it.
💡 Going further: Glycemic index and glycemic load shows how to calculate and compare this effect food by food, and Hidden carbs: the perfect-score trap shows where these fast carbs most often hide on labels.
ℹ️ Sources
• Ludwig DS, The Glycemic Index: Physiological Mechanisms Relating to Obesity, Diabetes, and Cardiovascular Disease, JAMA, 2002.
• Association between glucose dips and hunger, ChroNu study, ScienceDirect, 2024.
• Liu Y. et al., Testing the carbohydrate-insulin model, Cell Metabolism, 2025.