Roughly the same weight showed striking differences in composition & performance. My almond porridge sustains me until lunch - & on occasions when I play tennis during the morning while consuming only water. After the 1 hour spike up to 7.4, my BG stayed at about 5.5.
The Tesco fruit/fibre cereal gave a massive spike to 14.3 & by 11 o'clock had dropped to 4.1 & I was beginning to feel shaky. Happily at that point my reserves came into use & raised the BG to 4.7.
A further point of interest is that the Tesco data is for a suggested amount of 30 g, with 125 ml milk. That provides only 183 kcals, or 10% of the daily requirement - which does not amount to a substantial or even adequate breakfast.
I won't bore you with warnings of the dangers of "breakdown of vital muscle & body tissues" or "increased risk of heart disease, cancers & bowel disorders" or "the risk of kidney disease." Such a diet may be "suitable ... with medical supervision & with guidance from a state-registered dietitian."
A key paragraph is: "Research into the long-term effects of low-carb diets is now required. And in response to this, Diabetes UK is funding such research."