Speaking from personal experience, those symptoms sound a lot like an anxiety/panic attack. Stress, overexertion, undereating/overfasting, caffeine/stimulants, or some other problem with your endocrine system may cause this. Also, hypoglycemia may cause anxiety attacks as epinephrine is released in response to the drop in blood glucose; if you're experiencing this after eating it may be reactive hypoglycemia.

I've had anxiety attacks due to one or a combination of the following: too much caffeine, sleep deprivation, and fasting/undereating with overexercising.

My recommendations:

1.) If hypoglycemic, take necessary actions to remedy insulin resistance, diabetes, etc. 2.) If not hypoglycemic, stop fasting for a while, eat 3 moderate sized regular meals a day temporarily, strictly paleo, but avoid zero-carb/VLC (get 50-150g clean paleo carbs customized to what you think is appropriate for your current body). Eat at maintenance calories or more. 3.) Get 8-10 hours of good sleep in a regular pattern every day. 4.) cut down exercises (intensity and frequency) to only 2 a week temporarily (or go 1-2 weeks without deliberate exercise to recover). 5.) avoid caffeine and other stimulants. 6.) supplement with minerals (ZMA, natural calm, ...)

That's all I got, hope it helps.

Elevated heart rate is a common side effect of a food allergy. Work to eat foods in isolation for about a week or so and take your resting heart rate before and after you eat the different kinds of protein for starters. Take your heart rate every 10 minutes for the hour following, though you may get results in less of a close watch if you can feel it so strongly. Wearing a heart rate monitor is probably easiest.

You can be allergic to ANYTHING that has any amount of protein in it (that means most fats are innocuous, though it's possible that you just have fat-consumption anxiety, the reaction isn't to the actual food)- so this can mean meat, veggies, fruits, nuts, seeds, etc.

Keep us posted.

MCTs still do this to me today.

Fructose used to... I eliminated it so no longer an issue for me

I would lean towards MCTs or food allergy

Are you eating too much saturaed fat? That happens to me when I eat, like, about 600-1000 calories of heavy cream... Don't know what it is -- I stoppped eating a low-carb diet almost a year ago so never investigated. Vasoconstriction? Chylomicrons overload? Don't know. Have some starch with you meals...

Could it just be a surge of energy hitting you? Some people feel a nervous feeling after excitatory drugs. If you eat a lot of protein, it can have a thermogenic effect. You might want to keep a food log and look for patterns.

Happens to me when I eat cream and no protein with it - I get an Insulin surge and then go Hypo for a bit - I know the answer for me is to cut the cream but finding that hard! So I make sure I have it with other food too

I used to get energetic, confident, calm, active, and alert after a high-fat meal. That sensation would last for four hours. At that time, I feel like I could do anything. My heart was racing. I feel that I'm confident enough to talk to anyone about anything. My mood was extremely calm. I couldn't get angry or offended when thinking about anything. I could walk or run around the house without any effort. I was very alert. I could notice anything. My vision was astonishing. I could notice any little sound and detect it.

That four hours was like euphoria. I felt like a god. But after that, I would crash and return to my old normal self—a shy, depressed, and tiresome man.

But as I tried eating high-fat meals again and again, that euphoric sensation will diminish and I wouldn't feel the effect anymore.

But the interesting thing is that I wasn't eating coconut oil any other saturated fat. I was just eating olive oil to achieve that euphoria!

I also had this problem when I first started paleo. I had some increadibly pesky GI issues though and going back to hypoglicemia and bloating was not an option so I poked around online and read that some people got relief from GI issues by taking enzymes. I hate taking any kind of pill but I was pretty despererate and probably undernourished despite eating tons of food. That was the most beneficial thing I could have done because I was just not reaping the benefits of paleo/primal until I started taking enzymes. My panic attacks dissapeared as well as a number of other health issues. I took them with every meal for less than a month and weaned myself off and only take them if I eat too late or too much now. Also I've found that staying away from stimulants like chocolate, coffee and tea are essential for managing any kind of anxiety problem.