First, a person using this statement is usually not eating everything in moderation. It's just an excuse for indulging in bad foods. In order to eat everything in moderation, all foods must be eaten: including meats, grains, fruits, vegetables, fats, spices, herbs, and all the chemicals the companies have as food additives. With over 50,000 available fruits and vegetables alone, we start to see the problem. The average person only eats between 40 and 50 different types of food in their life.
Next, what defines moderation? Even though this myth of moderation had been busted long ago, people cling to the phrase without knowing what it means. Even when it was promoted by the government, they didn't define it. Is moderation a teaspoon, an ounce, a pinch, a pound? When it comes to fruits, like apples, moderation has been judged at 1 per day, or about 6 oz. Yet, arsenic is fatal at a few parts per million, or so small a quantity it can't be seen. And the pesticide, glyphosate (aka Round Up) has been shown to cause damage to the human body in the part per billion! Yet, both arsenic and glyphosate are added to processed foods and can be measured in the parts per thousand or 1000 times the safe limit.
Finally, there is no dietary need for sugar, chemicals, colorings, refined wheat and hydrogenated fats. Not only is there no dietary need, these have been shown to damage the body in minute amounts. When I hear a person using the term 'moderation', it's usually just before biting into a confectionery loaded with sugar, bad fats, and chemicals. What I hear a person really saying is that the momentary pleasure of eating the treat is worth the years of suffering later on.
Is it OK to have a treat now and then? Of course it is. Most nutritionist agree that about 1 serving (about 4 oz) 1-2 times per week is not harmful when a person is eating a diet rich in vegetables, fruits, quality meats and 100% whole grains, is free of processed foods and chemicals and the person exercises regularly.
I've never met a person who eats healthy use the phrase 'everything in moderation'.
Remember the qualifiers: First, a healthy diet is based on fruits and vegetables, quality meats, and 100% whole grains. The diet should be free of all processed foods and added chemicals. Also, the person should be exercising several times per week. Once this is fulfilled, then indulgences can take place. Indulgences cannot take the place of healthy foods.
The best type of indulgences are made with simple ingredients, that even a child can pronounce and that can be made at home. I make rich, dark chocolate chip cookies on rare occasions from 100% whole wheat flour, real dark chocolate and ingredients I get from a local farm. They are rich and very delicious. Since they are so tasty, I don't need more that one small cookie to be satisfied. It's all natural. Yes, it is a treat, an indulgence, but I know this type of indulgence is not going to harm me in the long run.
source : The Moderation Myth - Why It Doesn't Work