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University of Sydney: Lack of Protein Drives Overeating in Humans

Published on November 18, 2013,

New research from the University of Sydney’s Charles Perkins Centre and published in Obesity Reviews suggests humans’ instinctive appetite for protein is so powerful that we are driven to continue eating until we get the right amount of protein, even if it means consuming far more energy than we need…

The University of Sydney logo

The University of Sydney (Photo credit: Wikipedia)

Published online in Obesity Reviews, the research shows the overriding drive for dietary protein could be a key factor in the global obesity epidemic, with individuals’ total energy intake increasing as the percentage of protein in their diets decreases.

Regardless of weight, age or the time frame of a diet, the research found for the first time that reducing the percentage of dietary protein will result in increased total energy intake, contributing to overweight and obesity.

The research collated the results of 38 published experimental trials measuring the unrestricted energy intake of people on different diets, also taking into account a broad spectrum of age ranges, Body Mass Indexes (BMIs) and diet durations.

“We found that regardless of your age or BMI, your appetite for protein is so strong that you will keep eating until you get enough protein, which could mean you’re eating much more than you should,” says Dr Alison Gosby, lead author of the research and a Postdoctoral Fellow at the University of Sydney’s Charles Perkins Centre.

As diets shift towards an increased proportion of foods that are higher in carbohydrate or fat, available protein is reduced and energy intake necessarily increases.

“For example, when you consume things like soft drinks, which are fairly low in proportion of protein but high in calories, your energy intake will increase because you’ll need to keep eating to get the protein you need. If you add a soft drink to your lunch then you’ve added a lot of calories, but you’ll still have to eat the same amount of food.”

“The strength of our nutritional drive for protein is frightening within our nutritional environment, where there are a large number of low-protein foods consumed on a regular basis,” Dr Gosby says…

More at:  Lack of protein drives overeating

Can High Intensity Interval Training Help Suppress Appetite?

Published on September 18, 2013,

Most people would agree that exercise is generally a good thing but whether it actually helps weight loss is much less clear. Once reason is that exercising makes people feel hungrier and this in turn can make them eat more. However, new research discussed by Dr Briffa suggests one form of exercise – HIIT – might have the opposite effect and actually suppress the appetite. This is from Dr Briffa…

A US Marine Doing Pull-ups.

A US Marine Doing Pull-ups. (Photo credit: Wikipedia)

The heightened hunger that can come as a result of exercise does not happen to everyone, but my experience tells me it tends to be more common in individuals who engage in relatively prolonged exercise such as extended running or cycling. In my book Escape the Diet Trap I made the observation that ‘high intensity intermittent exercise’ (short, intense bursts of activity interspersed with longer periods of rest) tended not to make people hungrier.

Now, recently, a study was published which lends at least some support to these observations.

In this research, overweight, sedentary men were (at different times) subjected each of the following conditions:

1. continuous exercise at 60 per cent of maximum oxygen utilisation (VO2 max) for 30 minutes

2. 1 minute at 100 per cent VO2 max alternating with 4 minutes of 50 per cent VO2 max, repeated for a total exercise time of 30 minutes

3. 15 seconds of exercise at 170 per cent VO2 max alternating with 60 seconds at 32 per cent VO2 max for a total of 30 minutes

4. Rest (no exercise) for 30 minutes

After each condition, the men were fed a meal with a set number of calories. 70 minutes later, they were given access to food that they could eat freely. Food intake and activity levels were monitored on the day of each experiment and the following day (a total of 38 hours).

Interestingly, the intakes of the test meal 70 minutes after conditions 2 and 3 were lower than that when no exercise was taken (condition 4).

Also, energy intake over 38 was lower after condition 3 than after conditions 1 and 4.

Interestingly, I think, after condition 4, levels of the appetite-stimulating hormone ghrelin were lower, and blood sugar levels higher, than after the other conditions. Levels of lactate were also higher, and there is some evidence that lactate suppresses appetite [2].

This study was short, in that each condition was only tested once. However, there is at least some evidence here to support the idea that high-intensity exercise not only may not stimulate the appetite, but might even suppress it.

More (including references for the research) at:  Evidence suggests one form of exercise might actually suppress appetite

How To Lose Weight: Avoid Artificial Sweeteners

Published on November 29, 2012,

In the latest of his excellent and sometimes surprising tips on how to lose weight, the Diet Doctor says we should avoid artificial sweeteners because studies show they can actually increase appetite and cravings for sweet food. This is from the Diet Doctor…

Artificial Sweeteners - Splenda & Equal

Artificial Sweeteners – Splenda & Equal (Photo credit: Bukowsky18)

Many people replace sugar with artificial sweeteners in the belief that this will reduce their calorie intake and cause weight loss. It sounds plausible. Several studies, however, have failed to show any positive effect on weight loss by consuming artificial sweeteners instead of plain sugar.

Instead, according to scientific studies, artificial sweeteners can increase appetite and maintain cravings for sweet food.

This could be because the body increases insulin secretion in anticipation that the sugar will appear in the blood. When this doesn’t happen, blood sugar drops and hunger increases. Whether this chain of events really take place is somewhat unclear (although something odd happened when I tested Pepsi Max). Nevertheless, artificial sweeteners can maintain an addiction to sweets and lead to snack cravings. And the long term effects of consuming artificial sweeteners are unknown.

By the way, Stevia is marketed as a natural alternative to artificial sweeteners. That’s marketing talk. There is nothing natural about a processed super-sweet white powder like Stevia.

If you’re having trouble losing weight I suggest that you completely avoid sweeteners. As a bonus you’ll soon start to enjoy the natural sweetness of real food, once you’re no longer adapted to the overpowering artificial sweetness of junk food and “diet” sodas.

See all the Diet Doctor’s weight loss tips at  his ‘How To Lose Weight’ page

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