Final answer:
Janet can lose fat by maintaining a calorie deficit, meaning burning more calories than she consumes. To lose 1 kg of fat, she would need to have a deficit of approximately 37,000 kJ, which could take around 37 days with a daily deficit of 1,000 kJ.
Step-by-step explanation:
When considering weight loss through calorie deficit and exercise, as in Janet's case, we must understand how energy balance affects body fat levels. If Janet expends more energy through exercise and daily activities than she consumes from her diet, her body will metabolize stored body fat to cover the shortfall.
For instance, if she burns 13,000 kJ of energy but only consumes 12,000 kJ, she would be in a deficit of 1,000 kJ. Since about 37,000 kJ is equivalent to approximately 1 kilogram of body fat, a consistent daily deficit of 1,000 kJ could result in a fat loss of about 1 kg every 37 days, provided that this deficit is maintained daily.
To lose 30lbs (approximately 13.6 kg), Janet would need to maintain a similar deficit for an extended period. In addition to reducing calorie intake, regular physical activity such as bicycling can help create this energy shortfall.
The exact amount of bicycling required to burn an additional 1,000 kJ depends on factors such as body weight and intensity of exercise. Generally, it can take around 1 hour of moderate-intensity cycling to burn approximately 1,000 kJ.