What helped me to flip the switch is understanding the reality of my existing health and as not denying that I am getting older, as I age, I am finding my recovery and strength rebuilding process takes much longer than before. Also, setting realistic goals is helping me to keep the flipped switch in the "on" position.

Several things flipped my switch.

1. Failing health is very motivating, seeing condition reversal is also.
2. Changing my relationship with food. My personal mantra: "Use food as love to love yourself from the outside in so that your body loves you back from the inside out". Seeing the purpose of food as nourishment. When you eat bad food, your brain may jump up & down but your body is crying. I look at food & ask 'is my body going to love me back or cry.' "I love my body too much to eat that".
3. Kitchen purge
4. Meal planning/prepping takes the guesswork out of what to eat.

Daily desire to feel comfortable, functional in body and mind. Long range hope to attain a higher level of discipline and health.

The bottomline is if I don't eat healthy meals and make time for exercise, I don't feel as energized or have that sense of well-being. That is my motivation. My goal, as a Nutritionist, who counsels people who struggle with weight loss, is to find meals that a person can do realistically and enjoy. The same thing goes for exercise - it helps to be committed to a regular exercise, whatever it is, that will you stay disciplined. The health pay-offs are endless.

In my case there was no flipping a switch. I was in the United States Marines for 40 years so exercise is part of my life. Since I have a PhD in Nutritional Science and Doctorate in Naturopathic Medicine I always believed in practicing what I preach or in this case teach to my patients. I am far from doing it all perfect but I do try my best.

Even as a fitness trainer and nutrition coach, the motivation to make the right health choices on a consistent basis, varies up and down over time. This seems to be the one constant: your motivation will change over time. For me, the one thing that keeps me coming back to making good choices on a regular basis, is knowing what it feels like when everything works well. When you've had periods where you feel pretty good, your body functions pretty well, and/or you've felt not too bad about how you look, the memory of that is enough to bring you back to healthy choices. This is especially true when you've stopped making as many consistent healthy choices, and you start feeling crappy. Swings and roundabouts. But making sure to anchor the realisation that if you've felt, functioned, or looked good before, you can achieve that again and again.

For me personally, I suffered from disordered eating habits and poor body image as a teenager and young adult because I was attempting to reach "health" in all the wrong ways.Through severe calorie restriction and obsessive exercise, I thought that I was achieving "health" in the pursuit of thinness. It was not until I went to school to become a Registered Dietitian Nutritionist that a switch flipped for me. I learned that health is so much more than our physical appearance, and learned that the pursuit of health should not be based off body image and societies beauty ideals, but rather how the healthy behaviors I engage in leave me feeling mentally, physically, and emotionally.

Multiple factors, some mentioned above:

• Acceptance of aging--started at 40, hit home at 50! :)
• Having a child--wanting to be strong/healthy for parenting, being a good/healthy role model, living a longer/healthier life so I get to experience her life with her
• Watching my parents age
• Identifying an auto-immune disease (for me) or food allergy, etc. (for others)
• Finding joy in cooking and prepping food ahead of time or in bulk
• Time spent in the kitchen with a loved one

The problem with obesity can either be the end result from a variety of factors or the side effect. Some of the contributing factors for obesity is heredity, eating to many high calorie foods, too much of a sedentary lifestyle, lack of exercise (technology could be seen as a contributing factor to this). For example, more people are sitting down in front of a computer for 4- 8 sometimes 12 hours a day with very little movement other than getting up to eat breakfast, lunch or dinner, depending on what type of job they are doing and it that job includes shift work. (working 7a-3p, 3p-11p, 11p-7a, or 12 hour work day). Working a rotating schedule or working steady night shift will and cause some people to be less active in order to attempt to get more sleep due to the rotating schedule. This could cause people to eat and drink more fast food and more sugary/caffeine rich foods/drinks to counteract their sleepiness or sluggishness. The United States has an abundance of processed foods and access to many fast food restaurants. We are in a society built on convenience and "I'm always in a hurry" to do things or to get somewhere (work, school, take kids to sports practice) that it leaves the average American very little time to take care of themselves. As we age it is harder to get to a gym or workout, there is less time to eat healthy. More people are allergic to foods now than in the 1970's or 1980's. This could be caused by GMO's (genetically modified organisms) to make growing food faster and more abundant. Today there are more organic foods, more fitness centers, more food allergies, more diseases, more medicines, more vaccines, more technology, more pollution. All could be a potential cause of obesity. Yet many people are becoming obese while less are becoming healthy. More healthy living needs to be promoted by Doctors, other healthcare providers, the food industry, and by the company's who employee workers. Some people become obese due to having several physical injuries that cause them to be bedridden for months on end. For some of these people that can fully recover or mostly recover can lose the excess weight and be healthy again. For some who end up with chronic pain and physical disabilities this obesity struggle could last a lifetime even with exercise (physical therapy, nutrition counselling, a support system of family and medical professionals). Being overweight can lead to being at increased risk for or being diagnosed with high blood pressure, heart disease or diabetes or both. This can also lead to lower back pain, hip, knee, ankle (joint pain) do to the extra weight and strain being placed on these joints.

Stay well, create a routine making this fun somehow, reward yourself time to time, be flexible. Keep track of the results to measure changes, work with friends.

I made a decision years ago to invest in my health because it was very important to longevity and I wanted to make sure I had a lot of years to enjoy my children.

For me a simple and applicable solution that makes healthy meals planning easy is what makes it work

Reading about "How to be healthy is of no value whatsoever. Every patient gets handed a brochure of proper lifestyle, avoiding obesity; and the obesity rate climbs.
What is needed is a specific set of actions. Even a placebo that you take one 3x a day before meals can work if the action if followed. Keeping a diary works because then the BRAIN kicks in to help.
Whether it is saying a prayer, or doing jumping jacks, by following a specific set of actions allows the brain to release the proper chemicals.
Medicine is at fault for not understanding WHY placebos work: simply that the brain is directed to release the proper chemistry. In my book, "Stressed? Anxiety? Your Cure is in the Mirror" there are multiple ACTIONS to follow for these problems.
Telling a person to avoid stress -see 100+ books on Amazon is worthless without the actions to follow.

For me, there has not really been a point that i would say that "something flipped the switch" per say, growing up with a dad with diabetes and hypertension made me kind of want to stay in the right path and has kept me consistent for years. But basically, as a nutritionist i have counselled a couple of people and most of their moment came at the realisation that they may be suffering from a particular ailment. In Nigeria, basically eating right means a different thing for a lot of people and putting on weight was seen as a sign of "wealth". So here, the dynamics are kind of different because of societal expectations and the likes. so for most people the realisation that they may be suffering from say "diabetes" becomes their eureka moment and that keeps them consistent.

One very common cause of obesity is poor sleep, snoring and sleep apnea. This is a vicious cycle: the more you snore, the more fatigue in the AM and the need for cookies. The extra cookies are deposited as fat in the soft palate and throat tissues. What is worse, the significant other, whose sleep is impaired to the companion's snoring, also enters into this cycle! Yes, snoring is contagious.
The number of our patients who have successfully lost weight in order to stop snoring is very small; it is necessary to clear the snoring first.
Clear the nose/sinuses, reduce throat flab with pulsed irrigation, reduce the flab with tongue exercises.
Any social snoring can lead to very serious sleep apnea, so best to treat this early.

It's not only healthy food but exercises also. It's a combination of both.  
Though there are several motivations few of them are just to look around and you'll find people in your friend circle or in the family are suffering in different ways because of health. 
I experienced that keeping small goals always help the only thing is you need to be consistent. The best thing if you can find your loved ones to be part of your routine.