Women need Honesty. Men need self-restraint.

As a Man, you can't be afraid to sacrifice having her body for telling her the Truth.

At times, the Truth can be painful. Her immediate response will be to cut you off from her sensuality.

If you are an effective communicator, the wait time will be minimal. 

You must demonstrate to her that her long term well being means more to you than your short term sensory experience.

If you fail to emphasize this commitment to her long term through sacrificial actions, she will learn to manipulate this base desire. Effectively, you will be playing poker with all your cards showing.

This is the meaning behind "Tricking:" Using emotional and sexual manipulation to extort for material and emotional gain.

This relationship is intrinsically tilted in the favor of the manipulator using their body. This happens with men, also, but it is much more prevalent among women. 

Case in point: 

"Does this dress make me look fat?"

Why does this question perplex men so much? I submit the tension arises beneath the superficiality of her appearance. 

The underlying question is does she trust you to be honest enough to offer her critique?

If not, then are you capable of using compliments effectively as a means of distracting her from her temporary low self esteem?

Popularly, men fumble and bumble between compliment and critique, appearing to her as indecisive and inauthentic. That's more frustrating than being told coldly about her excessive weight (if applicable).

Another point worth further investigating is how, in retrospect, she feels you have been proactive in helping her maintain her health related goals.

Are you offering to workout with her? Do you cook meals that are healthier for her instead of her having to bring home fast food? Do you attend her Weight Watcher classes?

In my experience, this is very uncommon. 

Men, at times, can suffer from inattentive affection. Being able to be caught in such a "gotcha" moment is self evidently a lack of attention being paid to her and her desires for herself.

For men who are attentive to their women, no temporary moment of low self esteem catches them off guard. They know just what to say if it arises, and are proactive about participating in her life to prevent those moments from ever even happening.