Many things people put in their bodies are downright toxic.
Some, such as cigarettes, alcohol and abusive drugs, are also highly addictive, making it hard for people to give them up or avoid them.
If you have a problem with one of these substances, then diet and exercise are the least of your worries.
While alcohol is fine in moderation for those who can tolerate it, tobacco and abusive drugs are bad for everyone.
But an even more common problem today is eating unhealthy, disease-promoting junk foods.
If you want to gain optimal health, you need to minimize your consumption of these foods.
Probably the single most effective change you can make to improve your diet is to cut back on processed, packaged foods.
This can be tough because many of these foods are designed to be extremely tasty and very hard to resist.
When it comes to specific ingredients, added sugars are among the worst. These include sucrose and high-fructose corn syrup.
Both can wreak havoc on your metabolism when consumed in excess, though some people can tolerate moderate amounts.
In addition, it’s a good idea to avoid all trans fats, which are found in some types of margarine and packaged baked foods.