A good diet and exercise are very effective ways of controlling diabetes, probably as good as Metformin, better some people claim, but it is important to understand that 'liver dump' is perfectly normal and happens at regular intervals. It is nothing to do with diabetes.
All humans function within narrow ranges for many values, body temperature, glucose levels, salt and iron levels, hydration and so on. Nothing is ever constant and your body's own homeostatic processes attempt to keep it within strict ranges. Consequently, there are small fluctuations. Take body temperature for example. Below is a graph of how this fluctuates during the day:
Blood glucose levels fluctuate in a similar way but are complex because we eat at regular intervals, ie adding to the total store and we are active, depleting the total store. Nonetheless, if you ate nothing and laid in bed for several days, your body will keep you within the same limits. For most type 2 diabetics on meds like metformin, the problem is hyperglycaemia, ie stopping the BG level going too high, because something is wrong with the insulin response. Most of these people do not have to concern themselves with hypoglycaemia because the gluconeogenic response is fine. Hypoglycaemia is a problem faced by those who take stronger meds or insulin. They do need to be careful. Normally:
At about 3.8 Glucagon is released.
At about 4.6 Insulin secretion decreases
At about 5.5 Insulin secretion increases
At > 8.0 the renal threshold for glucose is passed and the excess starts to be urinated out of the system.
The 'Happy Zone' is 4.6 to 5.5 but, because we eat and work and play the body has upper and lower limit safety valves.
Below is a graph of someone with diabetes showing how BG levels fluctuate when monitored by CGM and finger prick. Notice that meal times increase the overall level, too much in the case of a diabetic, because the insulin response is not adequate, but notice how it also starts to go up whenever it gets low, even when nothing is eaten.
