Even if his theory is correct, it focuses on only a very small subset of the issues that could potentially cause weight gain.
The reason nobody has been able to produce a single bulletproof theory on weight gain is due to the fact that there is no single cause. Weight gain is the result of many potential causes:
Excess Catabolism of Muscle Mass:
Many people say that running (aerobically) is effective for weight loss but there is a case where it isn't. For instance, say you routinely run vary long distances but don't consume enough calories to sustain the energy... What happens is, your body will kick into catabolic metabolism and start using your muscle as energy. Less muscle means your caloric expenditure decreases. That means that you will have to start eating even less to maintain your current weight in response to the physiological changes. If you don't, whatever energy you consume that your body doesn't immediately use is stored as fat. Body fat is not necessarily bad as it creates a buffer between an empty tank of available energy and catabolism.
Ever wonder why people who take up extreme dieting can never keep it off in the long term? One possible reason is that they have cut their caloric intake too much. Initially, your metabolism will continue to burn energy at the same rate resulting in quick fat mass losses (ex a 1500 KCal diet). But, your body's number one concern is survival and it will adjust to the changes in food intake. In the long term your metabolism will lower to the point where, if you do eat a 'normal' meal your body will store as much excess energy (in the form of fat) as physically possible.
I have experimented with this to a small extent. I wanted to see how effective I could lose some fat mass with no exercise (I weighed 185 at the time whereas 170 is my 'healthy weight'). I have always been one of those 'you have to workout to lose weight' types so it was more of an experiment than anything.
Let me tell you, it wasn't fun. Not only did I put on weight faster than I ever had before when I started eating normal again but I was freezing all the time (and I'm one of those guys who never gets cold).
If you genetically have a hormone balance or you live an unhealthy lifestyle you can throw your hormones into a tailspin. By unhealthy lifestyle I'm referring to sleep deprivation and/or obesity. Your body returns your hormones to a healthy state while you sleep, especially the hormones that control hunger, metabolism, and weight gain/loss. See my answer here for a more detailed breakdown. If you gain too much fat mass your body will also start to produce less testosterone and more estrogen. Hormone balance is partially to blame for what people call 'man boobs'.
Eating Too Much
I know everybody pulls the 'eat less' card but there's more to the relationship between weight gain and eating too much. I attempt to sum it up here.
First, humans are a pretty versatile animal. Like pigs, we can survive off of just about anything as our digestive systems are very versatile at converting a wide range of different foods into energy. What most people don't consider is the amount of energy present in the food we eat.
Consider this, a seed has enough energy to sustain a plant's full germination until it grows large enough to send roots down and leaves up (over the period of days-months). That's a lot of energy and we eat them by the shovel full. Just the fact that we provide ourselves with such large quantities of food with little/no effort involved in obtaining such food is a risk factor all on it's own.
Many people preach whole bread as a healthy alternative to white bread. In reality it isn't really. You're still eating flour (which is just crushed wheat seeds) except with the outer husk of the wheat included in the mix. You could eat a white bread sandwich of grass from your lawn and get the same affect (dogs eat grass all the time for the same reason). Fiber is good for keeping things moving well through your digestive system but in the end you're just eating ruffage that your body can't digest.
Eating Too Fast
Second, digestion is chemistry and chemistry takes time. When was the last time you had a camp fire. Remember how long it took to burn a log? Now, consider that fire is an extremely fast process of converting energy to heat and it still takes hours to break down a log of wood. Now consider that digestion is a similar but much slower process. True, chewing helps you get their quicker but in the end it still takes hours to completely digest food from beginning to end (depending on what type of food).
Now, take into consideration that our body doesn't know how much we eat until it can digest some of the food and trigger a response. In fact, it takes until about 15-20 minutes after you start eating until you really start to feel satisfied. Unless you are eating pure sugar (which is digested much faster).
You literally may be full for 15 minutes before you know it and continue to keep eating. Especially if you are eating dense foods like carbohydrates and protein (which take much longer to break down). Take your time eating and you won't eat so much that you feel sick afterward.
If you want to curb your hunger quickly but still enjoy a full meal, consider a light serving of an appetizer containing fat and/or sugar to satisfy your appetite so you don't end up wolfing down large quantities of high carb food during the main course.
This list is just the start... There is no 'magical cause' to accumulating fat mass. Increased fat mass production is simply a product of many different bodily reactions to your environment.
If you want to improve your diet to lose fat mass I have a simple formula:
Get Over Your Anthropocentric Self. Take a minute to get comfortable with the fact that you are an animal. Our bodies have an amazing capacity to adapt to maximize the resources at our expense. If fat mass loss is your goal then stop and consider 'what type of environment do I need to be in to have an active healthy body' with a low fat percentage. I can give you a clue, it has nothing to do with living in a temperature controlled building, sitting 95+% of the time with an inexhaustable source of food within reach.