The most common response to the idea that a whole-food, plant-based diet is an optimal diet for people is —“everything in moderation.” This response is almost universal.
It is a philosophical debate – and I am not convinced it is a great life principle.
The same argument was used in in the 1950s and 1960s to convince people to reduce smoking. After all, you would not want to deprive people of the “solace, relaxation and enjoyment to mankind” that smoking has provided for more than 300 years. These days, doctors do not suggest that people reduce smoking but to stop.
One significant difference in the diet of the Japanese is the reduced amount of animal-sourced foods.
Even Moderate Meat Consumption is Detrimental
Seventh-day Adventist Studies show that those eating meat less than once a week have a higher health risk than those eating no meat for a number of common ailments. 
|Cause of Mortality||Lacto-ovo-vegetarian||Vegan|
|Ischemic heart disease||0.82||0.90|
Odds ratios of selected diseases by vegetarian status in California Seventh-day Adventists
Note that non-vegetarian Adventists are healthier than the average American.
A Taiwanese Buddhist study compared type 2 diabetes outcomes for vegetarians (consuming eggs and dairy with no fish or no meat) with non-vegetarians. The non-vegetarians consumed a limited amount of meat products. 
- Meat intake for females: 50% consumed less than 10 g/day; 25% consumed less than 2 g/day.
- Meat intake for males: 50% consumed less than 20 g/day; 25% consumed less than 7 g/day.
- Fish and meat intake for females: 50% consumed less than 17 g/day; 25% consumed less than 3 g/day
- Fish and meat intake for males: 50% consumed less than 37 g/day; 25% consumed less than 11 g/day.
One Big Mac, with 2 meat patties, contains 90 g of meat—so the participants were consuming only a very small amount of meat.
Despite this, there were still significant difference between the two groups. The odds ratio for males was 0.49 and 0.26 for females. So the male lacto-ovo-vegetarian participants had approximately 50% of the risk of diabetes with the females having 25% of the risk compared to those on a non-vegetarian diet.
We Have Evolved to Eat Plant Foods
As Bill Roberts, a pathologist, cardiologist and long-time editor to the American Journal of Cardiology, wrote:
Our closest relatives, gorillas, orangutans, bonobos, and chimpanzees are all primarily plant-eating animals.
Our stomachs, intestines, jaws and hands have evolved to gather and eat plants. Try wrestling a pig to the ground with your bare hands and making a meal out of it.
Breaking a Habit
Given that even moderate or minimal eating of meat is detrimental, there is no benefit in eating meat. Changing any habit can be difficult—and breaking a habit by reducing its consumption is impossible. As Plutarch pointed out, we had to learn to eat the gore and flesh of a dead creature.
- Tobacco Industry Research Committee (1954) A Frank Statement to Cigarette Smokers.
- World Health Organization (2015) WHO Life Expectancy By Country 2015. Available from: http://apps.who.int/gho/data/node.main.688 (Accessed 21 September 2016).
- World Lung Foundation (2015) World Cigarette Consumption. [online]. Available from: tobaccoatlas.org/topic/consumption/
- Fraser, G. E. (1999) Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists. The American Journal of Clinical Nutrition. 70 (3), 532s–538s.
- Chiu, T. H. T. et al. (2014) Taiwanese Vegetarians and Omnivores: Dietary Composition, Prevalence of Diabetes and IFG Marià Alemany (ed.). PLoS ONE. 9 (2), e88547
- Roberts, W. C. (1991) We think we are one, we act as if we are one, but we are not one. American Journal of Cardiology. 66 (10), 896.