She saw her first nutritionist at age nine when she tipped the scales at 120 pounds, and described herself as the biggest kid in all of her grade school classes. An admitted emotional eater, Zentner would turn to ice cream to soothe her sorrows following social or academic failures or a bad day at work.
By age 31, she was pre-diabetic with high blood pressure — and in the worst shape of her life.
Zentner's personal struggles are laid bare in her new book "The Weight-Loss Prescription" (Penguin). She also outlines strategies to help individuals break the cycle of poor eating habits and physical inactivity and encourage healthier relationships with food.
The Vancouver-based obesity specialist who practises internal medicine says she felt it "absolutely necessary" to share her own story and those of her patients in the book.
"Unfortunately, in today's society, obesity is still very much viewed as a social condition and not a disease, and we very much blame the patient," the 41-year-old said during a recent visit to Toronto.
"I wanted a book that wasn't just a how-to, but also to teach a component of empathy. I wanted there to be stories where people wouldn't just adopt a healthier lifestyle, but that they would identify with others in their struggle. And if it wasn't their struggle, I want them to develop a sense of empathy."
Zentner recalls in the book barely being able to walk five minutes on the elliptical when she first started. Over time, that number gradually rose in small increments until she was spending an hour a day on the trainer.
She and her husband eliminated their twice-weekly Chinese food takeout habit and she stopped "eating candies by the bagful," opting for fruit at dinner rather than ice cream.
Zentner would go on to lose 40 pounds within six months, and has dropped more than 175 in total.
She commutes to work by bike and has gone on to complete feats of endurance that would have once seemed impossible, from recently running a marathon in Honolulu to climbing Mount Kilimanjaro.
"As I say to patients, this disease isn't your fault but it is your responsibility," says Zentner, medical correspondent for Global National.
"I wanted people to know that if I could take the responsibility and still keep at it a decade later and be more enthusiastic about it and more passionate about it a decade in than I was when I first started ... then maybe they could too."
Zentner said she makes the assumption in the book that it's not the startup of a new diet that's the issue but "the mid-game," along with the lack of a cohesive plan to maintain the regimen long-term.
So, rather than adopting a one size fits all model, she encourages individuals to follow a structure for improved eating habits in keeping with their existing behaviour patterns.
Zentner defines and offers specific tips for those who fall under various eating personalities: the emotional eater, the calorie drinker, the fast-food junkie, the all-or-nothing dieter, the portion distorter and the sitting duck.
Whether using old-fashioned pen and paper or a digital app, she also emphasizes the value of keeping a food diary to discern eating patterns and look at where individuals may be falling short in meeting their targets.
"Part of maintaining (your lifestyle change) is looking at who you are and what your behaviour patterns are now instead of `That's what I want,'" says Zentner, who was the medical expert on CBC reality series "Village on a Diet."
"You have to see what your capabilities are and what the map looks like before you can even imagine getting to the destination. But I think we often — especially in this weight-loss world — we focus so much on the destination, this elusive kind of number."
Zentner says it's also incredibly important for individuals not to "diet in silence."
In addition to stating their intentions towards healthier living, she says people should draw on outside support to help them along their journey — one they don't have to embark on alone.
She points to one example in the book of a female patient who is married with three young boys and would typically order three pizzas, cheesy bread and chicken wings four nights a week.
They now order in just one night a week, trade cheesy bread for salad, nix the chicken wings entirely and eliminate leftovers by opting for an extra-large pizza. A second evening is devoted to homemade pizzas made from whole wheat pitas which Zentner says has become "the best night in the house."
"You make health the norm and everything else is a deviation."
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