[1]: http://www.nytimes.com/2013/02/13/opinion/calorie-detective....
Eating a caloric deficit will predictably result in weight loss, but there is some feedback between diet and resting energy expenditure (REE). The macronutrient balance you eat can affect REE.
https://jama.jamanetwork.com/article.aspx?articleid=1199154#...
> Among overweight and obese young adults compared with pre–weight-loss energy expenditure, isocaloric feeding following 10% to 15% weight loss resulted in decreases in REE and TEE that were greatest with the low-fat diet, intermediate with the low–glycemic index diet, and least with the very low-carbohydrate diet.
Because diet can affect REE, you can change your diet isocalorically yet still gain or lose weight. Your particular example seems to be an example of this, but the effect is likely very exaggerated. Differences are on the order of 10%, not 30%.
TL;DR: eating less carbs makes you burn more energy.
Funny you should say that when this was just published today: http://arstechnica.com/science/2016/01/why-the-calorie-is-br...