**Answer:**

Obesity occurs due to **(a) overeating of carbohydrates and fats**. This means that consuming an excessive amount of carbohydrates and fats can lead to obesity.

**Explanation:**

Obesity is a medical condition characterized by an excess accumulation of body fat. It is primarily caused by an imbalance between calorie intake and calorie expenditure. When we consume more calories than our body needs for daily activities and metabolic functions, the excess calories are stored as fat, leading to weight gain and eventually obesity.

Carbohydrates and fats are two types of macronutrients that provide energy to the body. However, if we consume an excessive amount of carbohydrates and fats, our body is unable to burn all the calories obtained from these nutrients, and the excess calories are stored as fat in adipose tissue.

**Overeating Carbohydrates:**

Carbohydrates are an essential source of energy for the body. However, consuming too many carbohydrates, especially those with high glycemic index such as refined sugars and processed grains, can lead to weight gain. These carbohydrates are quickly digested and absorbed, causing a rapid increase in blood sugar levels. As a result, the body releases insulin to lower blood sugar levels, which promotes fat storage.

**Overeating Fats:**

Fats are another macronutrient that provides energy and plays a vital role in various bodily functions. However, consuming excessive amounts of unhealthy fats, such as saturated and trans fats found in fried foods, processed snacks, and fatty meats, can contribute to obesity. These fats are high in calories and take longer to digest, leading to a slower metabolic rate and increased fat storage.

**Conclusion:**

In conclusion, obesity occurs due to overeating of carbohydrates and fats. It is important to maintain a balanced diet and consume these macronutrients in moderation to prevent excessive calorie intake and weight gain. A healthy diet should consist of a variety of nutrient-dense foods, including lean proteins, whole grains, fruits, vegetables, and healthy fats, while avoiding excessive consumption of high-calorie and processed foods. Regular physical activity is also crucial for maintaining a healthy weight and preventing obesity.

The answer is A