Final answer:
Eating only McDonald's for 30 days can lead to emotional and behavioral changes such as increased cravings for unhealthy foods, mood swings, and weight gain.
Step-by-step explanation:
Eating nothing but McDonald's for 30 days resulted in emotional and behavioral changes for Morgan, the subject of the experiment. One possible emotional change Morgan may have experienced is increased cravings for unhealthy foods, as fast food is often high in sugar, salt, and fat. He may have also experienced mood swings and irritability due to changes in blood sugar levels and nutrient deficiencies. Behaviorally, Morgan may have developed a dependence on fast food and an unhealthy relationship with food, leading to overeating and weight gain.