We already know that a slower metabolism can lead to weight gain. Just to enforce the issue and clearly state what foods are most likely to slow your metabolism, these are the worst culprits: processed foods, fat, sugars, and foods with trans fats. Within these categories are hot dogs, sugar-laden cereals, cakes, cookies, crackers, peanut butter, packaged foods, soy sauce, fried foods, butter, and cream. While this is not a comprehensive list, it includes some of the worst offenders.

Some foods contain goitrogens which are substances that interfere with proper functioning of the thyroid. This can lead to hypothyroidism, which can cause weight gain. These foods are healthy as long as they are not causing a disruption in the thyroid gland, and they include soybeans, Brussels sprouts, turnips, mustard, peanuts, radishes, broccoli, and strawberries.