Rule of thumb or rule of hand? When eating at a restaurant or away from home, use your own fist to estimate portion sizes for both animal protein and vegetables. One “fist” sized portion of protein with an equal size of vegetables is ideal during your weight loss phase.
Eat foods as close to where they were grown or picked as possible to maximize freshness. Frozen foods can be good choices since they are frozen right after picking. Because of the shipping time required to imported fresh fruits and vegetables, the nutritional content can suffer.
After being on dozens of diets focused on calories or portion controls or points or eating special “food” packaged for one program or other, the fundamental question remains. Do calories matter? Yes, calories or portions still matter but not as much as what the calories are and how your calorie choices impact your hormones.
Recommended reference book: Gary Taubes, Good Calories, Bad Calories, Anchor, 2008