Hello and Welcome,
How healthy you are (or how healthy you become) is largely determined by your diet and lifestyle choices. This is not an all-or-nothing proposition, but a continuum along which many paths exist which will lead you to improved health.
If you are in poor health, a single high-fat meal can trigger a heart attack. (Some of the people on this board have experienced this.) On the other hand if you are in fairly good health, you can get by with some 'exceptions' to Dr McDougall's diet plan. You must decide for yourself how many exceptions are reasonable, based on how healthy you are and how healthy you want to become.
For myself, I follow the Maximum Weight Loss plan most of the time. Although I am at a healthy BMI and my cholesterol, blood pressure, and triglycerides are low, I ate the Standard American Diet (SAD) for many, many years and I suspect that I have some degree of arterial blockage. I am trying to reverse that blockage. With that said, my goal is to follow McDougall's recommendations 98% of the time (1 or 2 off-plan meals per month).
I recommend you read the following Jeff Novick thread. It is long, but highly detailed and may help you with your choices.
Perspective of Dr. Lisle's "Continuum of Evil"?You may also be interested in the following threads:
Triage Your Health Efforts: The Good, The Bad & The UglyThe Real Dirty Dozen: The 12 Deadliest Lifestyle FactorsAlso, be sure to check out Jeff Novick's fora:
Greetings & Hot TopicsNutrition & Health FAQ: Answers To The Most Asked QuestionsBest of luck,
Cheers,
EDIT - added a link to Jeff Novick's "Perspective of Dr. Lisle's "Continuum of Evil"?
"Before Enlightenment chop wood, carry water. After Enlightenment chop wood, carry water." -- Zen proverb