That’s not a proper spike - and I say that as someone with Type 1 diabetes. It’s normal for your blood sugar to go up after eating. More than that, your graph shows a very quick insulin response - ie things are working well.
The drop into the red you mention isn’t actually ‘red’ at all - unless you’re on insulin and thus at risk of hypos. People without diabetes often go into the 3s. It’s only a risk for those on meds like insulin as, unlike non-diabetics, our blood sugar won’t stop there but can continue to go down, potentially leading to hypoglycaemia, seizures, etc. More then that, the Libre and other CGMs often over-estimate low blood sugars and that’s why people with diabetes are told to fingerprick to check what their blood sugar actually is.
I certainly don’t think everyone should get a CGM! They’re making money from the worried well and helping to spread silly ideas about food. Because I have diabetes, people sometimes ask me about their blood sugar, having bought a Libre or other CGM. The questions they ask are usually…well, neurotic. All based on the normal movement of blood sugar up and down.
I could write a book about it. No, actually, I could write a book wibbling on about blood sugar in normal healthy people, list lots of daft rules - and make a fortune from it like some popular influencers.
Anyone wondering what a healthy diet is, can look at the Mediterranean Diet, which has been shown to be one of the healthiest. They can also look at How Not To Die, which contains loads of studies. That diet is plant-based, which some people won’t like or won’t be able to do, but taking that diet and adding a bit of animal protein is one way forward. People are joking about beans and pulses above. Check out the Blue Zones programmes and books.
I think the problem with diet is extremes. People don’t want to only eat the perfect healthy foods, so they think “F* it! I might as well eat what I want” then over-indulge in addictive junk food. The answer is a middle way. Base your diet on healthy foods and have occasional treats.