To understand how to slim thighs you need to understand a little about how your thigh is constructed, i.e. thigh anatomy. There are several layers that go into making your thigh. The first layer is obviously skin. Under the skin is a layer of fat. The yellow colored stuff you can see in the picture is fat. This thigh fat surrounds the thigh muscles. When you gain weight, that yellow layer gets much thicker making your thigh bigger. The red colored stuff under the fat is muscle. When you exercise these muscles in a certain way, they get larger, which in turn makes the thighs bigger. That’s why, when wanting to slim thighs, you need to think about both thigh fat and thigh muscle. Both go up and down in size, influencing the proportions of your thighs.