Final answer:
The scenario most likely to result in burning more fat during a 30-minute exercise compared to rest is increasing the exercise intensity beyond 4 times BMR, as it significantly increases energy expenditure.
Step-by-step explanation:
To determine which scenario is most likely to result in burning more fat during a 30-minute exercise compared to 30 minutes at rest, we must understand how different factors can influence metabolism and fat burn. Here's an analysis of the given scenarios:
- Increasing the exercise intensity beyond 4 times Basal Metabolic Rate (BMR) will dramatically increase energy expenditure and is the most effective way to increase fat metabolism over a short period, such as 30 minutes, especially if the energy consumed is less than the energy expended.
- Decreasing the exercise duration to 15 minutes will likely result in less fat burned compared to 30 minutes since the total amount of energy expenditure would be lower.
- Consuming a high-carbohydrate meal before exercise could potentially provide more glucose for immediate energy use, which might decrease the use of fats for energy momentarily, resulting in less fat burn.
- Maintaining the same exercise intensity while increasing the percentage of kcals from carbohydrates could lead to a similar situation as the aforementioned point. The body may preferentially burn glucose from the carbohydrates instead of fat.
Given these points, the scenario most likely to result in burning more fat during a 30-minute exercise is increasing the exercise intensity beyond 4 times BMR.