The Reaction Range Theory states that genetics determine the range of possible heights, weights, IQs, etc. a person can exhibit (known as the reaction range), while environmental factors such as nutrition and disease determine the height, weight, IQ, etc. within the range. The scope of environmental factors that impact certain traits are dependent on the traits themselves; there is very little environmental influence on eye color, but there is a vast number of environmental factors that influence abstract reasoning.
The Nature v. Nurture argument is unproductive in this case. One does not dominate the other. Both serve important roles in determining a person's phenotype.
Person A's genetic IQ limits are 90 and 120. If person A grew up in a high quality, nurturing environment, he will reach closer to the top of his genetic potential (120). Person B's genetic IQ limits are 120 and 150. If person B grew up in a low quality environment, he will reach closer to the bottom of his genetic potential (120).
The obvious counterexample to this theory is obesity. We are not genetically predisposed to weigh over 400 pounds. This theory supports most, but not all traits.