Plain full-fat yogurt can be a part of a keto diet, but making homemade yogurt is the best way to lower (and control) the total carbs. If you buy yogurt, make sure you read the label carefully, as the total carb count - even with plain yogurt - can vary by yogurt brand. For flavored yogurt, make sure you go with a brand that is sugar-free. Even if it is labeled as such, look for added sugars and other ingredients that you may not wish to eat. Many sugar-free yogurt brands contain sucralose, which is an ingredient that many people choose to avoid.