With plenty of relationships flowing down to the drainage due to one of the oversized partners, the world has divided into the two ideological hemispheres— the one who speaks in the favor that bad body shape definitely kills their sexual desire and the other one who believes that the first group should be charged for fat shaming the oversized partners.
It depends on which side you want to stay, but I am here to discuss medical facts which could dispel all the doubts regarding body shape and sexual efficiency.
To shoot straight from the shoulders, I’d say— Yes, your deformed body affects the sexual intensity of not just you, but your partner as well.
Let’s go through how out of form body hinders the sex life.
When your body undergoes a sudden transformation, i.e., from toned or average body size to sudden heftiness, a lot of hormonal changes take place in the system.
Studies have denoted that the expanding body sizes have more cortisol level— the hormone responsible for restoring the sadness and anxiety in the body. 
So, even if you stand against fat-shaming, your cortisol level would poke you against your ideology.
With the higher level of cortisol, your confidence is likely to get jolted, and you start despising your attributes which were your strength once.
The negative perception about yourself can shatter your self-belief, and with such mindframe, you will never enjoy sex.
Probably, this is the reason why most of the women after delivery feel under-confident and tear off their own sex life by their hands.
You may aspire to have durable sex with your partner, but your shape might hamper your sexual energy.
Sex is as good an activity like playing, running, swimming, and the fitter you stay, the better you have it.
The energy imbalance in the body causes the larger waist circumference and body.
When you intake more food than the needed, the body stores energy in the form of fats.
The high-fat diets have earned a bad reputation in damaging physical endurance. 
To prolong your sexual session, you need to cut off the weight.
No matter what’s your opinion about body shape, it definitely affects your performance, and have a terrible cascading effect on your partner.
An excellent sexual session demands an unoccupied brain which is good enough to focus on sex.
With high flabby flesh around the body, you are conditioned to think about your partner’s satisfaction.
Your consciousness might urge you to think “does my partner still love me,” “am I good enough for my partner,” etc.
You might also establish insecurity where you’d be forced to believe that your mating partner might dump you due to the lost beauty.
As the number of thoughts progress in your mind, you move a step forward in disturbing your sex life.
Our body needs a transparent state of mind for sex because it is probably the only activity whose productivity increases without deploying our brains.
Degraded sex experience
I have a problem with the people who define quality sex depending on the prolonged sex indulgence.
For me, good sex is all about satisfying your partner and yourself without harboring any guilt, sadness, low confidence, etc. after the orgasm.
However, with your brain engaged in the myriads of thoughts, there are fewer chances that you’d be able to meet the desires of your partner.
Your experience is what defines your quality, and your weight issues have a lot of psychological, physical, and sexual drawbacks.
If your partner entices you to shed weight, they are not necessarily shaming your shape. Bulkiness brings no good to the body, and it may be your partner’s general concern. Sensing fat-shame in every move and taking pride in an unhealthy diet will only affect your comforts.