Complex sentence: Usually a big sample of data is collected-this would require verification, validation and recording before the analysis can take measure and study the relationship between dietary intake and measurable physiological effects such as weight loss, controlling for other key variables such as exercise.
Split into simpler sentences: Usually a big sample of data is collected-this would require verification, validation and recording before the analysis can take place. In the field of health, for example, researchers might measure and study the relationship between dietary intake and measurable physiological effects such as weight loss, controlling for other key variables such as exercise.