Before you brush this off as just another fad, she notes that unlike other popular diets such as Atkins and Paleo, the hydrophilic diet plan allows for all food groups, including carbs and fruit. Animal proteins are fine. The foundation of the diet is high-hydrophilic fruits, vegetables, and legumes such as chia seeds, okra, oats, pears, barley, Brussels sprouts, kidney beans, chick peas, oranges and agar.

The secret of these foods lies in what's more commonly known as soluble fibre.

"When ingested soluble fibres dissolve they form a gel in our intestines," says Gilbert, a registered dietitian and certified nutritionist from New York state in the US. "The gel is the key to steadying blood sugar and thus diminishing cravings, keeping you full, and maintaining digestive health."

Hydrophilic foods shouldn't be confused with foods with high water content such as tomatoes, cucumber, watercress, watermelon and pineapple. Such foods, though "HD friendly", says Gilbert, lack water soluble fibre and will leave you feeling hungry soon after you eat them.

Think of hydrophilic foods as a hard, dry sponge next to your kitchen sink. Add a little water and it's instantly revitalised and ready to use.

"The hydrophilic foods on my plan will have the same effect on you," she says.

Chia seeds are "the quintessential hydrophilic food", says Gilbert. A chia seed has the capacity to absorb up to 12 times its weight in water. The high-fibre seeds are native to Mexico and Guatemala, and reportedly were a staple for the Aztecs.

In the Asian diet, hydrophilic foods include snow peas, baak choy, napa cabbage, seaweed, edamame, shirataki noodles and kelp noodles.

Gilbert created the hydrophilic diet in 2010, but the idea of using such water-loving foods to aid weight loss is a little older. Since the mid-2000s, the gelatinous agar has been a dieter's favourite, particularly in Japan.

Called in Japanese, agar is derived from red algae and has been popular across Asia for centuries as an ingredient in desserts and to thicken soups, sauces or preserves. At 80 per cent fibre and with virtually no calories, carbs, sugar or fat, it bulks up in the gut and promotes the feeling of fullness.

A study by Japanese researchers published in the journal in 2005 looked at the effect of the kanten diet on obese patients with impaired glucose tolerance and type-2 diabetes. Seventy-six patients were randomly assigned to either a conventional diet or a conventional diet with agar. Both groups were on these diets for 12 weeks. The researchers concluded that the agar diet resulted in marked weight loss due to the maintenance of reduced calorie intake and an improvement in metabolic parameters.

Of course, agar aside, health experts have long espoused the benefits of a diet rich in soluble fibre, not only for weight control, but also to aid in diabetes control and lower LDL ("bad") cholesterol.

Gilbert, however, has sexed up soluble fibre with a fancy name and iPhone app that grades meals according to how hydrophilic they are. In her new book, to be published by health and wellness publishers Rodale, she presents her diet as a total mind-body approach.

"I integrated the metaphorical meaning of the term hydrophilic as well to elicit a change in our state of mind - a necessity when you make a life adjustment," says Gilbert. "The HD diet is logical and spiritual and that is why it works."

The 12-week diet begins with a two-week "start strong" phase that encourages a balanced diet solely based on consuming high-hydrophilic and HD-friendly foods. In phases two and three, "IFs", or infrequent foods such as white bread, processed foods and refined sugar, are slowly introduced but only in limited amounts.

Ordinary dishes can be turned into a hydrophilic meal simply by substituting some ingredients. For example, a salad of iceberg lettuce, tomatoes, cucumber and grilled chicken could change to a salad of kale, bean sprouts, cabbage, carrots, snow peas and grilled chicken.

Some of Gilbert's clients have lost up to 14 kilograms over the 12-week regimen.

"While my clients may lose more or less, as a general rule, 20 to 25 pounds [9kg to 11kg] is a successful weight loss for the 12-week period," Gilbert says.

"The weight absolutely stays off because the HD diet is a lifestyle where habits are relearned; not a fad that is restrictive and unsustainable."

Her book offers motivational stories from clients, detailed shopping lists, daily menu templates and a strong emphasis on making healthy decisions for life.

It's best not to overdo fibre, though. Consuming fibre in excess may cause bloating, cramps, gas and diarrhoea, says Charmain Tan, a registered dietitian and founder of Seventeen Nutrition Consultants. She advises that if you're trying to boost fibre in your diet, do it gradually and drink plenty of fluids to help pass the fibre through the digestive system.

The US Institute of Medicine recommends a daily fibre intake of 38 grams and 25 grams respectively for men and women 50 years and younger, and 30 grams and 21 grams per day for those over 50. As a gauge, a tablespoon of chia seeds has five grams and a pear three grams of fibre.

"Unfortunately, none of my clients have eaten enough fibre," says Tan.

"Many studies have shown that the general public does not consume enough fibre." 

Foods that make you feel full longer

Trying to lose weight? Have more of these water-loving ingredients on your plate

Chia seeds

These seeds can absorb water up to 12 times their weight. They are packed with antioxidants, fibre, iron, magnesium, calcium, omega-3s and potassium.

Okra

The goo from this low-calorie vegetable is used as a thickener for soups and stews. It's high in vitamins C, A, and B6, foliate, calcium, iron and magnesium.

Oatmeal

Watch oatmeal cooking on the stove and the gelling is immediately apparent. It's loaded with protein, phosphorus, potassium, selenium, manganese and iron. Steel-cut oats are best.

Pears

This fruit is filled with pectin, a complex carb found naturally in plant cell walls; it acts as a detoxifier, regulates the gastrointestinal tract and helps to stimulate the immune system.

Barley

This grain has a high water-absorbent capacity and is a good addition to a salad.

Kidney beans

All beans are hydrophilic. Kidney beans have a high antioxidant value and are an ideal protein replacement in salads.

Agar

A gelling agent made from seaweed, agar is 80 per cent soluble fibre. It reabsorbs glucose in the stomach, passes through the digestive system quickly and inhibits the body from retaining and storing excess fat.