Question: Do you see Echo Boomers as being more physically fit than their parents?
No (see Media Lies and Millennial Doting).
Now, let's say that you are in the fitness industry and you want to know if you're in a good industry to succeed (answer: yes). Because Generation Y is massive, even if an equal amount of Echo Boomer had interest in fitness on par with Generation X (hypothetically, let's say 20%), you would have triple the amount of customers in Generation Y. In other words, fitness has an advantage with Generation Y due to volume. However, obesity is rising in the United States, which indicates that an interest in fitness is not growing.
Logical Fallacy Warning:
What I've observed about fitness over the past five years is that the physically fit are beginning to increase their level of fitness. Similar to wealth, those who are fit continue to benefit from being fit (creating an interesting tautology), while those who are obese continue to increase their obesity. From a business perspective, this means that marketing heavy fitness programs to people at the gym will be more effective than marketing those programs to the obese.