Final answer:
The statement that weight loss or gain cannot be achieved by changing both caloric intake and output is false. Weight change occurs through a balance between the calories consumed and the energy expended, and adjusting both factors is often the most effective method.
Step-by-step explanation:
The statement 'Weight loss or gain can be achieved by changing caloric intake, changing caloric output, but not a combination of the two' is False. Weight change, be it loss or gain, can indeed be realized through adjusting both caloric intake and caloric output simultaneously. This is a fundamental concept of thermochemistry relating to the body's balance of energy consumed and expended.
The process of losing weight involves expending more energy than the calories consumed, which can be achieved through a combination of consuming fewer calories and increasing physical activity. By contrast, gaining weight would require consuming more calories than the amount of energy expended. These principles apply to the body's metabolic processes, including how the body metabolically adapts to changes in diet and exercise, affecting the basal metabolic rate (BMR).
A balanced approach involving diet and exercise is often most effective for weight loss, as supported by scientific studies suggesting that a low-calorie, low-fat diet combined with moderate to high levels of physical activity is a proven strategy for achieving and maintaining weight loss.