Statistics show that although consumption of low-calorie, alternative sweeteners has gone up in each of the past five years, so has the percentage of the population that is obese. According to sugar manufacturers, this shows that the low-calorie, alternative sweeteners are not effective weight loss aids.

Which of the following assertions, if true, would most weaken the sugar manufacturers' conclusion?

【选项】Obesity has declined among people who have consistently used low-calorie, alternative sweeteners.