A Calorie Is Not a Calorie – Not Even Close
A calorie is not a calorie. Some calories may, for example, make you burn 300 more calories per day (corresponding to 30 minutes of running).
The figure above shows that a strict low-carbohydrate diet on average resulted in burning 300 calories more, compared to a diet much higher in carbohydrates. More details about the study here.
Recommended reading, especially for those who still believe Coca Cola’s favorite argument: There’s no bad food, only bad character.
The truth is that an exaggerated intake of sugary drinks may force you to run an extra 30 minutes a day to maintain your weight. If you don’t get hungrier from all the sugar and eat more (which many do), in which case you could need an extra hour of running – per day – to maintain your weight.
Exercise is great, but for maintaining weight it’s easier to avoid sugar and junk food.
And with regards to Andrew's comment, you are right that people will never agree in the diet world, but there are two reasons. Money and pride. You cite the infamously agresive, unpleasant and abrasive Dr McDougall (starch solution) and his follower, a fireman who wrote "engine2diet". Their diet is of course by far superior to the SAD diet, but what diet is not? Honestly, look at a picture of Dr McDougall and of his followers: a great many of them are cachexic. Not the picture of health. Rather than re-write the arguments here, I recommend you read the following posts: http://chriskresser.com/why-you-should-think-twice-about-vegetarian-a... AND http://authoritynutrition.com/top-11-biggest-lies-about-vegan-diets/. Chris and Kris nail it quite well. A vegan diet is non sustainable: it lacks B12, iron and vitamin D amongst other things.
There are facts based on good science and there are opinions. We are all allowed our opinions. What is sad is that some of us choose their facts to suit what they have decided to believe and reject all evidence presented to the contrary. You see this in peope who have built a career on an idea who have too much pride to say "I was wrong". You also see this in people who are paid big money by either "Big Food" or "Big Pharma" to give a message, regardless of the evidence. This is a form of moral prostitution.
Do not forget that most physicians and dietitians are totally unable to read a science article: they do not have the biostats and epi knowledge to be able to do so. They also have forgotten basic notions of biochemistry and are trained in thinking in the following way: a symptom, a diagnosis, a pill - or better, many pills. Lifestyle changes and diet are paid lip service and laughed upon. This is not "serious". Pills are.
Most physicians and dietiticans have to believe the conclusions of the authors. I have personal knowledge of this since I am a physician who for many years had to believe at face value what the authors of science papers said, just like all my colleagues (IF they had an interest in nutrition, which is rare). You also have to know that medical and dietitian education is paid for by big pharmaceutical companies and big food companies. The diabetic associations advice papers are written by people paid for by pepsico. Is it surprising they recommend a high carb intake? 80% carb? Sheer folly. Of course, we can live on such a diet, but how long and at what cost? Basic science has shown clearly that over 40% carbs, regardless of their source, there is an epigenetic switch to inflammation. Always. People like McDougall may choose to ignore this. They won't drop dead. But they'll get systemic inflammation. Regardless of what they think.
I took one year of epi and biostats training during a Masters in Public Health. I learned that unfortunately, most science was crap and paid for by people who had massive interest in certain conclusions. This is why I read basic science articles. They are less likely to be contaminated by financial pollution.
People like McDougall have chosen their camp and will never change, regardless of any evidence. McDougall has chosen to ignore that biochemical markers improve dramatically on a LCHF diet. And that weight goes naturally back to normal. Without effort. He would rather have his followers lose weight while starving and eating a tasteless low fat diet. Too bad McDougall chose to ignore that his brain, just like that of any human, is made of 3/4 fat. He probaby needs quite a bit, considering his irritability.
LCHF normalizes biochemical markers, improves dramatically epilepsy, autism, ADHD and Alzheimer's. Fatty liver is cured in days. HDL soars. LDL changes from small tight particles to big harmless fluffy particles. Triglycerides normalize. Gllycemia goes down to normal, so does HbA1C. If this is dangerous waters, I'll swim there with pleasure.
As to the maintainability of the diet, I suppose it varies person to person. I have been low carb for eight years and very low carb (ketogenic) for at least two years, with 0.6 mmol/l being my lowest recorded blood ketone level during this time and 5.4 mmol/L being my highest measured blood glucose (post-meal). I only started monitoring daily blood ketones two years ago, so I am not sure how ketogenic I was before two years ago. I find the diet is very easy to maintain. Eat lots of fat, modest meat head to tail, daily bone broth soups or sauces, use butter and olive oil sauces aplenty (Hollandaise, vinaigrette, mousseline etc.), avoid sugar, starch or vegetable oil, and treat sugary fruits and starchy vegetables as condiments. How much mustard or horseradish would you eat with a meal?