If you smoke or drink, no you may not receive a temple recommend to enter the Lord's Temple. But, some parts of the Word of Wisdom are not part of the temple recommend, but we are encouraged to practice such as eating right, exercise and plenty of rest. Althought we as LDS have been taught this for years, scientist and nutritionists are now seing the benefits of living this healthy lifestyle.
Personally, I think that the smoking, drugs and drinking are considered harsher due to the effect it can directly have on our spirits, compared to the "lesser" effect on the spirit our diets and exercise play. But, we all have our free agency to choose the path we chose to live. The Church of Jesus Christ of Latter Day Saints website