I would suggest having a careful look at the ingredient list on the shakes.
You may find that they keep calories low but are sweet to taste because they use artificial sweetners. –
– Our bodies are clever, because the amount of sugar which is normal to have circulating in the blood stream of the average adult is about a teaspoon. – Yes, 1 teaspoon diluted in 4.5 to 5.5 liters of blood, is normal, so you see why our bodies are designed to quickly respond to sugar in our diet. – As part of that response if we eat anything that tastes sweet our body starts to release insulin in preparation for the expected rise in sugar levels in the blood stream. – That is why artificial sweetners cause an insulin spike. And its the insulin levels that we are really trying to control.