One of my favorite nutrition guides, Catherine Shanahan, MD, wrote a book last year that I somehow missed until recently, The Fatburn Fix. I own one of her earlier books, Deep Nutrition, which is filled with great info, including how to look at folks and evaluate their genetic quality: Rate your friend’s kids! It’s really a tome, though, much too detailed for practical use. Which I always thought was unfortunate, since Dr. Cate started the slender athletes movement with the LA Lakers, so obviously has some practical advice to offer.

This newer book is shorter and much more accessible, although as a compulsive explainer, she does preface the how-to section with two others, i) why most of us are on the road to diabetes and ii) how the fat-burning mechanisms of the body are waylaid by popular eating habits. No guilt is implied. How can we figure out what we should eat when Big Food trumps the medical establishment on nutrition research? Billions spent on research–plus marketing and lobbying–have honed the production of food that makes us eat often and badly, while healthy nutrition researchers are poorly funded and mostly ignored by the medical establishment.

Dr. Cate is a doctor, not a prose stylist, but she occasionally comes up with a vivid metaphor, and that’s certainly what she needs when she’s trying to convince modern readers that food doesn’t provide energy. She reminds us to think of what happens to a wild animal that doesn’t have food.

What doesn’t happen: the animal calls Uber Eats.

I choose to envision a lioness, though a rabbit will do if you prefer something cuddly, or a bonobo, if you prefer something humanoid. I chose the lioness because I remember so many nature shows featuring an apex predator hunting for days without getting a kill. I used to think the editors were worried about the audience reaction when savanna Bambi gets asphyxiated by fangs clamping its throat closed. Now I’m thinking the portrayal is accurate. Yet the lioness never starves. She keeps hunting, day and night, as long as it takes, and eventually gets to eat. As does any animal, hunter or gatherer.

The lioness can keep moving because her energy is provided by burning body fat, and that’s how human bodies evolved to work, too. We can choke our fat-burning mechanisms by gorging on processed vegetable oils and excess sugars, or we can live like a lioness. Sort of. I have a high level of energy for staying on my feet all day on production lines or stocking shelves, without eating any extra meals or snacks, but I haven’t made any glorious kill bites lately.