High-sugar content

• Meals that include soda or other sugary drinks, cookies and cake can contribute to the post-meal slump. When the sugar enters your body, the hormone insulin is produced. When you eat increasing amounts of carbohydrate-rich food, larger amounts of insulin release and cause more of an amino acid called tryptophan to be absorbed into the brain. Tryptophan, in turn, can become either serotonin or melatonin, both with a role of inducing sleepiness. To avoid sleepiness, keep sugary foods to a minimum.
  
  

Lots of Carbohydrates

• The sleepiness-inducing effect of insulin also happens after you eat high carbohydrate meals.The carbohydrates in bread, chips and crackers have the same effect as sugar, releasing plenty of insulin while the carbohydrates are broken down and absorbed. Protein-rich or low-carbohydrate foods, like lean chicken, turkey, eggs, nuts and salad do not invite the same amount of insulin release and could help prevent some of the post-lunch slump.
  
  

High-Fat Meals

• Fast food might be convenient, but it doesn't hold much promise to help keep you awake. Researchers from the journal Physiology and Behavior found that eating a high-fat meal created even more feelings of drownsiness than eating a low-fat, high carbohydrate meal. The attribute sleepiness to the presence of CCK, a hormone that is naturally released after high fat meals. CCK digest fats but you can lessen the release if you eat smaller, lower fat meals.
  
  

Skipping Breakfast

• Getting too hungry can cause excessive hunger, which can in turn cause overeating. The Weight Loss Clinic at the WebMD website warns that the hunger from skipping breakfast can make midday cravings intense, causing an overdose of fatigue-inducing fatty, sugary foods. To avoid overdoing it at lunch, eat a solid, balanced breakfast.