The amount of glucose (sugar) in your blood changes throughout the day and night. Your levels will vary depending upon when, what and how much you have eaten, and whether or not you have exercised.
Fruits should be preferably taken in the morning, this helps in detoxification and also aids in weight loss. Although these benefits can be availed by having fruits anytime during the day, morning is said to be the ideal time for having fruits.
Most of the causes of hypothyroidism cannot be prevented, with the exception of medication-induced hypothyroidism and iodine deficiency, which are largely preventable.
The simplest thing you can do for better insulin sensitivity is to eat a high-protein, low-carb diet that favors a low-glycemic response. A number of recent studies have shown high-protein diets to be effective for weight loss because of how they support insulin health and better energy levels.