Sunday, 23 August 2015

Carbohydrate Restriction for Type 2 Diabetes.

We are often told to look to the £m charity Diabetes UK for dietary and other advice on receiving a diagnosis of Diabetes. As a pre-diabetic (HbA1C 38 mmol/mol or 5.8 % in old money) I did this and prepared a short summary :-

Monday, 17 August 2015

Hall shows greater weight loss on reduced carbohydrate

Data mining in Hall (2015) and ignoring the press and social media nonsense storm I find that in the (insulin sensitive) men the measured fat loss using the gold standard (?) DEXA method was actually marginally greater on the reduced carbohydrate diet :

Saturday, 15 August 2015

Short term weight loss in insulin sensitive men

Digging further into Kevin Hall's study it is apparent that the men and women were substantially different in terms of Insulin Resistance, Insulin and Leptin levels. The men average a HOMA-IR of 2.2 but the women average 3.3 putting the two genders either side of the 2.7 Insulin Resistance cut-off used in Brazil. Fasting insulin was 50% higher in the ladies and fasting leptin 2.5 times higher, but fasting blood glucose was the same in both at 88 mg/dl / 4.9 mmol/l.

The men tended to be older (38 vs 33) and less obese (34 vs 38 BMI) with p-value 0.15 or lower but not reaching statistical significance (9 women and 10 men is a modest sample size).

Friday, 14 August 2015

We need to talk about Kevin (Hall)

A few months ago I chewed over a poster presentation by Kevin Hall and associates which presented the findings of a detailed metabolic comparison over six days of an 800 calorie intake reduction of either carbohydrate or fat alone in a crossover design. I was concerned about an apparent imbalance in calories / carbohydrate balance that suggested the reduced carbohydrate (RC) phase was depleting glycogen reserves and hence the study was not of a steady state condition.

I general I like the work done by Hall as I have a similar modelling background. There are however remaining concerns now that the full version of the paper has been published in Cell Metabolism.

Firstly I would like to address the "pictorial abstract" :

On the left we can presume that the ~800 kcal/day reduction in dietary fat intake was replaced by fat from body stores, as everything else is shown as the same. At 9.4 kcal/g that's a fat loss of 85 grams/day which is in line with the stated "89 ± 6 g/day of fat loss" for the RF diet (at 9 kcal/g it's a near exact match). So far so good.

On the right life gets complicated. The reduction in carbohydrates allows fat oxidation to flourish to the tune of +400 kcal/day - the reason people like me favour carbohydrate restriction. So the subjects are burning 400 more of fat but 500 less of carbs and hence energy consumption has dropped by about 100 kcal/day. Although burning 500 kcal less of carbs the intake of CHO has been reduced by 800 kcal - so 300 kcal  ( 81 grams/day) has appeared out of the woodwork, or more likely out of the body's glycogen stores.

With 300 kcal of bonus fuel entering the mix the fat loss of the restricted carb diet is impaired - with the same fat intake it relies on increased oxidation and this only rose by ~400 kcal/d which is indeed only half of the reduction of intake seen in the fat restricted phase.

The question remains as to how long this condition could be sustained before the additional carbohydrate reserve dried up and forced a further increase in oxidation of fat. A study for 6 days isn't even half of the Atkins induction phase and the carbohydrate intake here was ~140 g/day which is well north of any "Low carbohydrate" diet let alone anything ketogenic.

A secondary question arises from the fact that supplementary table S3 shows that there was no significant fat loss in the female subjects on either diet - in fact their % body fat went up (NS). I shall be returning to this study to focus on the men who did at least lose weight and reduce their fat mass significantly. I always prefer single gender studies as so much variability is added and significance lost by combining men and women.

Monday, 3 August 2015

Why do the obese overeat ?

Another post inspired by a coincidence of two events - watching "65 Stone and Trapped In My House" and reading a couple of blogs after seeing Twitter references to them.

The TV programme was disturbing, to the extent where I nearly turned it off a couple of times. It centred on an obese man who had grown from 30 to 65 stone ( 910 lbs / 413 kg ) and become confined to one room in his own house and all but unable to move. Sadly the subject of the documentary died shortly after filming aged 33, from heart failure which was predicted by a bariatric surgeon who visited him for an assessment.

We saw the poor guy drinking full sugar pepsi while wallowing in his bed, and when his friends came round for dinner he wanted to eat the whole dish that they had made for sharing amongst five people.

Why does a man with at least 300 kg of fat stores feel the need to eat and drink 10,000 calories a day? When a dietitian suggested he would maintain at 7,000 and then should reduce by 1,000 per day in weekly steps he could not contemplate this and flat out refused - this was "too fast".

300 kg of fat stores is about 2.3 million calories so enough for 330 days energy supply at 7,000 a day. This is reminiscent of the infamous Scotsman "Mr AB" who did a water only fast for 342 days when faced with a similar dilemma - described here (including audio) and published by Stewart and Fleming. Unlike the unfortunate Carl Thompson (RIP) Mr AB lost 276 pounds, reaching his target weight of 180 pounds and maintaining the bulk of his weight loss. Over the five following years of observation, AB regained just sixteen pounds.

So what can we learn from a guy who on the night he died phoned a takeaway at 11pm to order apple crumble and two servings of ice cream, no doubt opening the conversation with his familiar "It's Carl and I'm starving". Was he suffering from persistent high levels of insulin, brought on by eating mountains of carbohydrate food, leading to much of his food intake being shuffled into fat stores leaving his metabolism still hungry ? This is the general statement of Gary Taubes' "Insulin Hypothesis" and further illustrated in Bob Briggs' Blog "Why are fat people hungry".

Bob quotes from the work of Dr Joseph Kraft who studies insulin levels and identified 4 patterns of insulin response to eating (the 5th pattern is minimal insulin response / Type 1 Diabetes) :
We know that fatter people generally have higher insulin levels and consequently release less fatty acids from storage into the bloodstream to use as metabolic fuel :
Also higher insulin levels reduce free fatty acid flux and concentration :
So the obese person with elevated insulin is denied access to the massive calorie reserves they are carrying and consequently live in a state of frequent hunger and consequent overeating with a proportion of what they eat being stored away as the carbohydrate portion further inhibits lipid oxidation.

The solution to unlocking the fat stores and reducing hungers lies in reducing insulin, through carbohydrate restriction and / or intermittent fasting. Even the Pattern 4 insulin response (green in the chart above) eventually falls after eating so a 16h fasting / 8h eating window approach may be beneficial.

The ketogenic diet, which is high in fat and low in carbohydrates, mimics the metabolic state of starvation, forcing the body to utilize fat as its primary source of energy. This also results in reduction in insulin levels. Once adapted to such a diet the consumers of an LCHF diet with moderate protein are, in general, not hungry, and frequently under-eat in clinical studies.

Evidence that carbohydrate restriction mimics total fasting has been provided by clinical studies where infusing lipids into the bloodstream at a rate equivalent to the Basal Metabolic Rate have little effect on outcomes - "carbohydrate restriction, not total energy restriction, is responsible for the increase in lipolytic sensitivity observed during fasting". S Klein and RR Wolfe have published several studies looking at lipolysis rates and the influence of various parameters on those rates.

From this and other reading I am drawn to conclude that :
  1. Lack of fat release from storage leaves the fat person needing to eat for energy supply. Persistent hunger is a powerful motivator especially in the lonely or depressed.
  2. Eating carbohydrates elevates insulin and reduces fat oxidation, reducing use of fats as well as their availability.
  3. Elevated insulin responsible for locking up the fat also stores further dietary fat on the body. Eating carbs and fat together maximises this effect.
  4. Carbohydrate restriction or fasting allows insulin levels to fall and unlock the fat reserves.
  5. People on total fasts or 500-800 calorie modified fasts, or carbohydrate restriction to ketogenic levels, are not hungry and therefore do not typically overeat.