Garlic and weight loss
Garlic (Allium sativum) is shown to be potent normalizer of lipid (fat) metabolism. It reduced overeating in diabetic experimental animals. Garlic extract supplementation was included in the clinical study of a very low carbohydrate diet and shown to significantly help in weight loss, along with other supplements like chromium, etc. The results were published in the American Journal of Medicine, 2002, Volume 113.
As to the way of taking garlic, it depends on several factors to be considered. The efficiency of any food depends on how it's prepared and eaten.
If you chew on a garlic clove, it becomes similar to minced garlic and can be expected to be absorbed equally well. On the other hand, swallowing a whole garlic clove can hardly be effective since its tough texture will prevent the beneficial nutrients from getting into its target organs and tissues.